|1980 Sigma D-10 Anniversary Guitar|
|Manufacturer||Sigma by C. F. Martin & Company|
Guitar maker C.F. Martin & Co., based in Nazareth, Pennsylvania, created a line of inexpensive guitars in 1970 to compete with the increasing number of imported guitars from Japan and elsewhere. The result was Sigma Guitars.
The Sigma line was discontinued by C.F. Martin & Co. in 2007.
In 2011 the German company "AMI Musical Instruments GmbH" purchased the rights to the name and relaunched Sigma Guitars again, this time being produced in China.
Initial construction was in Japan by various manufacturers/factories from 1970 through 1983.
The first Sigmas were typically dreadnought acoustics, although Grand Concert Series (GCS) and classical models were also produced from the early 1970s (1971) onward. Dreadnought models DM-5 and DR-7 are the most common early Sigma guitars until the late '70's. D for dreadnought, R for rosewood, M for mahogany and the number denoting the grade of wood, 5, 7, 9, 11, 15. 
Construction moved from Japan (1970–83), to Korea (1984-93/94), and finally Taiwan (1993–2007).
In 1980, model designations were added to capitalize on Martin model numbers: the DM-18, DM-19, DR-28, DR-28H, DR-35, DR-41, and DR-45. The DM-5 and DR-7, as well as other early models continued to be built during this time as well.
Headstocks & Logos
Sigma guitars made in Japan from 1970 through 1983.
- The early 70s models (1970 -1975) can be distinguished by a square headstock, shaped similarly to that of a spatula, the logo consisting of a gold decal with the single word SIGMA surmounted with the Σ symbol (the Greek letter sigma), in mother of pearl. The sigma symbol is often described as a "sideways M."
- Interestingly, while playing a Sigma guitar the "sideways M" becomes "right side up" suggesting "M" for Martin.
- By the mid 1970's (c1976) the headstock logo design changed to utilize a gold "Martin style" decal stating "Sigma Guitars" in script with "Est. 1970" underneath in a smaller block font. The headstock shape was also modified, tapered to more resemble a Martin guitars headstock.
- As is tradition in classical instruments, Sigma classical guitars do not have the headstock logo, and one must rely on the inner label for identification.
Labels and Brands
Sigma's made in Japan from 1970 through 1979 used a paper label to identify the model and serial number of the instrument.
- The earliest examples had a plain black on white inner paper label giving the model and serial numbers. These will show a 4-digit serial number.
- The next generation are transition labels that are white w/Sigma and three horizontal lines in gold ink, the Greek sigma in black and printed black text everywhere else. These will have a 4, 5 or 8 digit (7*0XXXXX) serial number stamped or hand written on them.
- Later labels (c1972 onward) are again white labels that had gold & black lettering with a border this time, often pinkish-brown or violet purple in color. All other text was printed in black ink, or stamped on in ink by the manufacturer (model and serial numbers.) 5-digit serial numbers.
From 1980 through 1983, the end of Japanese production, the back center brace is pressure stamped, or "branded" in a football shape stating Sigma Guitars/Made in Japan/For/C.F. Martin & Co. followed by an ink stamp of the model number, and prefixed by the serial number assigned to the instrument. (e.g. L-R as seen through the sound hole: Serial number, "Brand," Model number.) The serial numbers on these instruments were often preceded by a letter; e.g. S0XXXXX.
Early Korean made guitars show this same brand, only Made in Korea in place of Made in Japan.
Under the best of circumstances, Sigma serial numbers only provide an indicator of the year in which a particular model was built. This may be due to them being built in several Japanese factories at the same time with no coordination or tracking in the numbering system.  However, while some models lasted the entire run from 1970 through 1983, others did not and were only offered for a limited number of years. Along with other physical indicators or attributes can help determine the approximate construction date of a particular example, but almost never exactly.
For example, serial numbers on the earliest DR-7's began using 4 digit numbers on through 5 digit numbers, with some early 70's models along the way with the unusual 7*0XXXXX, 8-digit system. (See below for that explanation.)
- One Original Sigma DR-7 owner stated "I have an old Sigma DR-7 Guitar....s/n 6860. I bought it new in 1970." Furthermore, DR-7's with a four digit ink stamped label serial number, a zero fret and an adjustable bridge saddle strongly suggests a very early ('70-'71) build date.
Some early 70s Sigma guitar serial numbers began with 7*0 suggesting the 197* build date (e.g. 750XXXXX possibly equates to a build year 1975.) These were eight digits long, the third digit always a place-holding 0, while all others by then were five digit serial numbers further adding to the confusion. It is widely assumed by owners and Sigma historians that this is correct, though C.F. Martin cannot, or will not confirm this.
"Sigma-Martin USA" guitars built in 1981 and 1982 had serial numbers 900,001 to 902,908. These serial numbers are documented by C.F. Martin & Co. and to this day, remain the only Sigma serial numbers that are.
- These "N" instruments of which there were only two models ever produced, the DR-28N & DR-35N imported partially assembled and finished from Japan to the Martin factory in Nazareth. There they were completed and finished alongside the regular production line.
- Necks and bridges were installed, as well final sanding and finishing before strings were installed and a final set-up was done. 
Serial numbers for Sigma guitars built in Korea, Taiwan and Indonesia are perhaps meaningless, though again some seem to indicate the year of manufacture (e.g. 81XXXXXX.) Since we know these instruments were manufactured from 1984 through 1993/4, and then 1994 through 2007 in these three countries, it is safe to assume that a serial number beginning with 81XXXXXX (which I have personally seen) was not produced in 1981.
In 1980 the paper labels were discontinued and the inner back brace was "branded." Later Korean production show a resurgence in the paper label system for model and serial number, sometimes along with the brand. These had an even fancier border. 
Sigma identified their dreadnought and grand concert guitars as "Second Generation" when the headstock design changed and began to utilize a gold decal stating "Sigma Guitars" in script with "Est. 1970" underneath in a smaller block font, in the familiar Martin headstock decal form. This may have been as early as 1976.
- re: My own first Sigma, a DM12-5, which I purchased new in mid-1977 (I still have the receipt) had this second gen "Martin style" decal logo. It being a smaller, local store, the instrument may have been sitting there for a while before I acquired it. While I cannot be absolutely certain of the year it was manufactured, it was certainly by, or prior to 1977.
High end models such as the D-10 Anniversary model have the "Second Generation" logo inlaid in the headstock using mother of pearl.
Some guitars made later in Taiwan and Indonesia have a different headstock decal: "Sigma Guitars" on top with a miniature version of the "C.F. Martin & Co." logo underneath. Some of these guitars also had the "Est 1970" instead of the C.F. Martin & Co.," using a slightly different block font that is both fatter & wider than the original 2nd gen instruments. The paper labels for model/serial number identification had also changed again, this time with a fancy border and the word "Sigma" or "Sigma Guitars" in gold ink.
The issue of whether or not Sigma guitars are solid wood or laminate wood has been a source of controversy and confusion for many years now. This is understandable since the Martin customer service department now responds to individual inquiries stating "all" Sigma's had laminate back/sides with solid tops, while Sigma catalogs from the early 70s list the back/side wood as solid.  
To complicate matters further, in the 70's Sigma produced a line of guitars clearly identified by Martin, at that time, as having laminate backs and sides: model numbers starting with 52S, e.g., 52SDM-5, 52SDR-7 and 52SGCS-7.
- The answer to the question "Are Sigma guitars solid wood or laminate?" is best answered "Yes." It is safest to assume that the Sigma in your hand is made of laminate sides and back, however it has also been said that some of the earliest Sigma's were made completely of solid woods.
Other Sigma instruments included mandolins, banjos, acoustic and electric basses and solid body and hollow body electric guitars. Some solid body electric guitars were made by Tokai Guitars Company, LTD.
After Sigma musical instruments were built in Japan, Korea, Taiwan and finally Indonesia, they were sent to Martin & Co. in Nazareth, Pennsylvania to be inspected and adjusted by Martin personnel before going to an authorized retail store for sale to the public. These inspections and adjustments were made in the "old" Martin building on North St. (c1865,) then known as the Import house.
The DR-28 was manufactured in Japan, Korea and Taiwan while the SDR-28 and the SDR-28H appear to have been manufactured in Korea and Taiwan only, starting in early 1984. The DR-28 was of a solid Spruce top with laminated Rosewood sides and back while the SDR-28 and SDR-28H was made with a solid Spruce top and solid Rosewood sides and back. The SDR-28 "C series" was manufactured with solid spruce top and solid rosewood back and sides. As of this writing, I have no information on the A or B series SDR-28s.
The DR-28 and SDR-28 and SDR-28H are clones to the original Martin D-28 and HD-28 guitars and are high quality instruments.
- It has been suggested that these SDR branded instruments were the precursor, or pilot program for what has now become C.F. Martins own in-house, less expensive, "X" series of laminated wood guitars.
Sigma also made a DR-28SC model manufactured in Japan and an SDR-28SC model made in Korea. SC stands for (Sunburst/Cutaway)
Martin discontinued the Sigma line in 2007, and in 2011 the German company "AMI Musical Instruments GmbH" (AMI) acquired the rights to the brand from C.F. Martin and relaunched Sigma Guitars worldwide. However, after a year or more of AMI energetically reviving the Sigma brand, with an extensive 75 model range of acoustic and electro acoustic instruments, all closely following Martin designs, it was discovered that C.F.Martin, having ceased production and marketing of Sigma Guitars in 2007, had, inexplicably allowed their rights to the Sigma brand name in US territories to lapse – (United States law states that: In contrast to copyright or patent law, trademark protection does not have a set duration or definite expiration date. Trademark rights … expire when the owner stops using the mark in commerce ……. federal trademark registrations expire ten years after the registration date, unless renewed within one year prior to the expiration – See: http://en.wikipedia.org/wiki/United_States_trademark_law#Limits_on_trademark_law) – Further, the US rights to the lapsed ‘Sigma’ brand name had, prior to C.F. Martins intended sale of brand to AMI, been revived by St Louis Music of Missouri, who currently offer a four model range of Martin clones, all sporting a ‘block style’ Sigma logo similar to that which appeared on the very early Japanese output marketed by C.F. Martin. As a result of this confused situation it has been necessary for AMI, and their US distributor Golden Ark Inc, to change the name under which their guitars are sold in USA to ‘Kindred Guitars’. This brand name appears to the left of the Sigma banner on the “http://www.sigma-guitars.com” website
Basic Characteristics of Made in Japan Sigma Guitars
From 1970 to approximately 1975:
- Adjustable bridge on all dreadnought (except DJ-7, Dreadnought/Jacaranda) and GCS (Grand Concert Series) models, but this too is an inconsistency as not all had the adjustable bridge.
- Peghead is a unique "spatula" shape that differs from the traditional Martin peghead design in that it is more square than tapered, as the later 2nd Gen models were. These 'spatula' shaped headstocks only lasted the first few years before taking on a more tapered appearance and shape.
- Original peghead logo Sigma with Greek symbol Σ above,
- Adjustable truss rod through peghead through 1979.
- The first year 1970 DR-7 has a zero fret as well as some of the 12-strings did to approximately 1973, or 1975 (DM12-5.)
- Early examples often have adjustable height bridge saddles as well. These were discontinued earlier in the 7 series 6-string models than the 5-series, 12-strings and other "lesser" models. Adjustable saddles are considered less desirable as they did not come in full contact with the bridge and soundboard, and therefore did not offer full sound or the best quality.
From approximately 1976 to 1983:
- Nonadjustable bridge, often showing a pair of pearloid screw covers.
- Martin style peghead (tapered)
- "Martin style" gold decal peghead logo stating "Sigma Guitars" in script with "Est. 1970" underneath in a smaller block font.
- In the early 1980s, some special instruments, such as the D-10 Anniversary, and DR-28H models, have an inset pearl/pearloid logo. The "Est. 1970" is underlined in these cases.
- Adjustable truss bar through peghead from 1970 through 1979. Truss rod adjustments were accessed through the sound hole from 1980 forward.
- From approximately 1980 through 1983, and in later Korean made instruments with few exceptions, stamps, or "brands" were embossed into the back brace wood instead of using a paper label. Labels would return later during the Korean years and continue through final production in Taiwan and Indonesia.
- There were only a few types of tuning machines used during these years. All were basic and inexpensive. There are three different shapes of the buttons on these tuners. Oval in the early models, a more square shape ala' Schaller in style in the middle years, and a keystone shape, or 'wing' on later versions.
- The lesser 6-string models, such as the DM Mahogany series, had open-backed, 3-on-a-plate non-adjustable "economy" tuners in the earliest years. Later ones, were individual machines, but looked exactly the same from the front.
- The 12-string models had open-back "6-on-a-plate" (non-adjustable/economy) tuners.
- More upscale models, such as the DR Rosewood series, had the same tuners only with chromed cover over them. These were all 'non-adjustable' and held in place by two opposing screws (corner to corner) on the back of the headstock. Styles of this type are still available today with only minor differences.
- Early Rosewood series model 12-string guitars (pre-1975) had non-adjustable covered "6-on-a-plate" ala' Kluson style  tuners. Later versions (approximately 1973 onward) were individual, non-adjustable, as on the 6-stringed models (14:1 ratio.) 
- Many 6-string "upscale" models from 1981-1983 instruments had adjustable sealed tuners, but the 12-string models continued with the covered (non-adjustable) "economy" tuners (14:1 ratio.) Others continued on using the cheaper tuners.
- The earliest sealed tuners, as early as 1972 (e.g. DR-9, DR-11) had a 6-sided cast body and no brand name (11:1 ratio,) while there were others later on that more resembled Schaller (stop screw to the inside, Schaller style buttons.) or Grover tuners (stop screw below but without the familiar crescent knob.) Few of these sealed tuners were branded at all, while others in later years show "Sigma" stamped on their backs.
Made in Japan Models
- CS-6 Classical guitar. Mosaic marquetry around sound hole. Rosewood bridge. Spruce top. Back and sides bubinga wood. Mahogany neck. Rosewood fingerboard. Pearloid buttons on tuners.
- CR-7 Classical guitar. Mosaic marquetry around sound hole. Back and sides rosewood. Top made of finest close-grained spruce. Carved peghead. Neck mahogany. Flat-oval neck. Top and back binding black and white. Lacquer finish.
- DM-5 Dreadnought. Solid spruce top. Mahogany back and sides with tri-layered black/white/black binding. Natowood neck. Unbound rosewood fingerboard. Nickel-silver frets. Open in-line tuning machines. Adjustable rosewood bridge on earliest examples. Adjustable truss rod through peghead from 1970 through 1979. Unbound peghead. Open tuners on early models. Covered "economy" tuners on later ones. High Gloss finish.
- DR-7 Dreadnought. Solid spruce top. Matched rosewood back and sides. Back and sides have 5-layered w/b/w/b/w binding. Rosewood overlay on peghead. Peghead bound in white. Adjustable truss rod through peghead from 1970 through 1979. Rosewood bridge and fingerboard. Adjustable rosewood bridge on the earliest models. Pearl/pearloid inlay position markers on fingerboard. Chrome closed back tuners (11:1 ratio.) The first year is known to have a zero fret. High gloss lacquer finish.
- 52SDR-9 Dreadnought (c1972.) Solid spruce top. Matched laminated rosewood sides and 3-piece back ala' D-35, however with a contrasting rosewood center strip. Back and sides have 5-layered w/b/w/b/w binding. Rosewood overlay on 1st generation "Spatula" headstock (Sigma w/Σ logo.) Headstock and fretboard are single-bound in white. Adjustable truss rod through peghead. Rosewood fingerboard. Non-adjustable rosewood bridge. "Snowflake" (more similar to a Maltese cross) pearl inlay position markers on fingerboard. Chrome closed back tuners (11:1 ratio.) High gloss lacquer finish.
- 52SDR-11 Dreadnought (c1972.) Solid spruce top. Matched laminated rosewood sides and 3-piece back ala' D-35. Back and sides have 5-layered w/b/w/b/w binding w/pearl. Rosewood overlay on 1st generation "Spatula" headstock (Sigma w/Σ logo.) Headstock and fretboard are single-bound in white. Mother of pearl trim throughout ala' Martin D-41. Adjustable truss rod through peghead. Rosewood fingerboard. Non-adjustable rosewood bridge. Mother of pearl Hexagon & heptagon inlay position markers on fingerboard. Gold plated closed back tuners (ratio unknown.) High gloss lacquer finish.
- DJ-7 Dreadnought. Solid spruce top. Brazilian jacaranda sides. 3 piece matched grain jacaranda back with marquetry. Peghead bound in white. Ebony fingerboard. Mother of pearl inlays on fingerboard. Fixed ebony bridge. Natowood neck. Adjustable truss rod. white/black/white binding. Satin lacquer finish.
- DM12-5 12 String Dreadnought. Solid spruce top. Mahogany back and sides. Tri-layered black/white/black binding on back and sides. Rosewood bridge and fingerboard, some had an "ebonized" bridge (blackened.) Unbound peghead and fingerboard. Pearl/pearloid position dots. Open inline "6-on-a-plate" tuning machines. Covered "economy" tuners on later examples. Adjustable rosewood bridge to approximately 1975, non-adjustable thereafter. Adjustable truss rod. Earliest models had a zero fret.
- DM12-7 12 String Dreadnought. Solid spruce top. Rosewood back and sides. Tri-layered white/black/white binding on back and sides. "Ebonized" (blackened) rosewood bridge and fingerboard on some, natural rosewood on others. Peghead and fingerboard bound in white. Pearl/pearloid position dots. Adjustable rosewood bridge to approximately 1975, non-adjustable thereafter. High gloss lacquer finish. Adjustable truss rod. Covered "economy" tuners. High Gloss finish.
Earliest models had a zero fret.
- GCS-6 Grand Concert. Solid spruce top. Mahogany wood back and sides with tri-layered black/white/black binding. Mahogany neck. Adjustable rosewood bridge. Peghead bound in white. Rosewood fingerboard. Adjustable rosewood bridge. Adjustable truss rod.
- GCS-7 Grand Concert. Solid spruce top. Rosewood back and sides. Tri-layered white/black/white binding on back and sides. Rosewood fingerboard. Adjustable rosewood bridge. Gloss lacquer finish. White bound peghead. Adjustable truss rod.
Additional Models Approximately 1975 to 1978
Some of these guitars still had the early peghead logo, instead of the "Second Generation Sigma" Martin style logo that started in approximately 1976.
- DT-22 Dreadnought. Spruce top. Tiger-striped maple sides and back. Maple veneer on Martin style peghead. Tortoise shell binding around back and sides. Black pickguard (later examples have Tortoise shell pickguards.) Fixed bridge, some with diamond shape inlays. Fingerboard has snowflake and diamond shape inlays. Pearl "SIGMA" block inlay between 19th and 20th fret. Later examples have gold plated, Sigma embossed Schaller style enclosed tuners (ratio unknown.)
- DR-7S Dreadnought sunburst. Martin style peghead bound in white. Spruce top. Rosewood back and sides. Rosewood fixed bridge. Adjustable truss rod.
- DM-5S Dreadnought sunburst. Unbound Martin style peghead. Spruce top. Mahogany back and sides. Rosewood fixed bridge. Adjustable truss rod.
- GCS-4 Grand Concert. Martin style peghead bound in white. Spruce top. Mahogany back and sides. Rosewood fixed bridge. Adjustable truss rod.
- CS-4 Classical Guitar. Spruce top. Mahogany back and sides. Mahogany neck. Rosewood fingerboard and bridge.
Sigma produced numerous "DR-*" models from the mid-70s on through 1984: DR-8; DR-9; DR-11; DR-14; DR-15; DR-28; DR-28S; SDR-28; DR-35; DR-41; and DR-45. The very rare DR-14 was often confused with the DR-41 but it was a different model. They have a 3 piece back, and the fret markers are different as well. These rare, hard to find models were actually made in Japan and imported to, and guaranteed by Levin in Sweden. They cost more than the top of the range DR-41 at the time. They have a paper label stating this and "Sigma Guitars" "est 1970" is inlaid on the headstock in abalone. There is a DR-14 on display in the Sigma Museum in Munich,Germany.
Special and Unusual Models
From 1980 through 1984, prior to construction being moved to Korea, Sigma produced several models that included electronic pickups: SE-18;SE-19; SE-28; SEMC-28 (with arched back); and SE-36. These models have saddles with each string individually compensated, yielding superb intonation. These models were produced in very limited quantities.
In the early 80s Martin imported partially assembled Sigma guitars from Japan and the assembly was completed in Nazareth, Pennsylvania. There were two models, labeled "Sigma Martin USA DR-28N and DR-35N," "N" for Nazareth. A Martin factory sales brochure shows the DR-28N to retail at $600.00 and the DR- 35N to retail at $650.00 The DR-35N has laminate rosewood back and sides and a solid spruce top.The DR-28Nhad a two piece back and the DR-35Nhad a three piece back (ala' Martin's own D-35.) The DR-35N had additional detail on the fretboard. The original factory brochure also states components were processed and finished on the same production line as regular Martins. The Head stock reads "Sigma Martin USA" and inside the sound box is " made in USA" with Martin address etc. Some consider the DR-35N to be a prototype of the inexpensive laminate Martin Shenandoah line of guitars. Since this model had serial numbers running from 900,001 to 902,908,. it appears that nearly 3000 Sigma Martin USA guitars were produced.
In 1980 Sigma produced a 'limited edition' of D-10 Anniversary model guitars to commemorate 10 years of Sigma production in Japan. The D-10 has a solid spruce top and laminate mahogany sides and back, rosewood fingerboard with diamond and square position markers, mother of pearl band stating "Anniversary" between the 19th and 20th fret, tortoiseshell type pickguard and binding, and close-ratio tuning machines. This limited production run lasted one year and this model remained on Sigma Dealers quarterly price lists from October 1980 until July 1981. It is unknown how many of these D-10 guitars were built but it is believed by some that production of the D-10 model ran into the thousands.
- Official Webside Sigma Guitars
- sigma guitars
- Sigma Catalog, dated June 1, 1974
- Sigma Catalog, date not listed, but prior to 1979 Second Generation.
- correspondence with C.F.Martin Guitar Co, Inc. Customer/Consumer Service Department, December 2008
- Sigma catalog, January 1984