Railroad chronometers, or Railroad Standard Watches, are specialized timepieces that once were crucial for safe and correct operation of trains in many countries. A system called Timetable and Train Order, which relied on highly accurate timekeeping, was used to ensure that two trains could not be on the same stretch of track at the same time.
Regulations of the watches used by critical personnel on the railroads (engineer, conductor, switch yard controllers, etc.) were specified almost from the beginning of widespread railroad use in the 1850s and 1860s. These regulations became more widespread and more specific as time went on, with some watches that were "railroad standard" in one time period falling away to no longer being qualified in others. There was no absolute, universal definition used across different railroad lines; each company appointed one or more "time inspectors" (typically a watchmaker) who decided which watches they would work on and accepted as usable. In the United States, the American Railway Association held a meeting in 1887, which resulted a fairly standardized set of requirements, but not all railroads adopted them.
Webb C. Ball
One notable watch inspector was Webb C. Ball. His first job as a time inspector was when he was brought in by the Lake Shore and Michigan Southern Railways in 1891 after a crash and was tasked with bringing their time inspection standards up to industry normals. Ball's career eventually led to him being the time inspector on more than half the United States' railways, leading to a far more uniform set of standards in the U.S.
A typical railroad's requirements for a watch in the early 20th century might include:
- only American-made watches may be used (depending on availability of spare parts)
- only open-faced dials, with the stem at 12 o'clock
- minimum of 17 functional jewels in the movement
- 16 or 18-size only
- maximum variation of 30 seconds (approximately 4 seconds daily) per weekly check
- watch adjusted to at least five positions: Face up and face down (the positions a watch might commonly take when laid on a flat surface); then crown up, crown pointing left, and crown pointing right (the positions a watch might commonly take in a pocket). Occasionally a sixth position, crown pointing down, would be included.
- adjusted for severe temperature variance and isochronism (variance in spring tension)
- indication of time with bold legible Arabic numerals, outer minute division, second dial, heavy hands,
- lever used to set the time (no risk of having the stem left out, thus inadvertently setting the watch to an erroneous time)
- Breguet balance spring
- micrometer adjustment regulator
- double roller escapement
- steel escape wheel
- anti-magnetic protection (after the advent of diesel-electric locomotives)
The minimum requirements were raised several times as watch-making technology progressed, and the watch companies produced newer, even more reliable models. By World War II, many railroads required watches that were of a much higher grade (as many as 23 jewels, for example) than those made to comply with the original 1891 standard.
The Waltham Watch Company and the Elgin Watch Company were both used as early as the 1860s and 1870s  as railroad standard watches. Later, Hamilton Watch Company, Illinois Watch Company and many of the other American watch manufacturers all produced railroad-grade watches.
- National Association of Watch and Clock Collectors "Railroad Time Service"
- Google Books - American Railway Association - "Historical Statement" Page 8
- National Museum of American History "Watch, Railroad Model Pocket Watch"
- National Association of Watch and Clock Collectors "Waltham Watches"
- The Elgin Watch Collectors Site "Elgin Watches"
- U. S. Naval Observatory "History"