In watch-making, or horology, a California dial refers to a clock face that consists of half Roman (usually 10 o'clock to 2 o'clock) and half Arabic numerals (usually 4 o'clock to 8 o'clock). Sometimes the hours of 3, 6, and 9 are replaced with a dash instead of a numeral and an inverted triangle in place of the 12. The use of this dial style dates back to the 1930s, for example in early Rolexes, Panerai, Glycine watch and Kampfschwimmer diver's watches. A number of Rolexes were refurbished by a company based in California using this style of dial, resulting in the name "California dial".
A modern example of a watch with a California dial is Nomos Glashütte's "Club Campus".