California dial watches

For most watch enthusiasts a "California dial" means a dial where the numerals are half Arabic and half Roman. The concept was patented by Rolex in 1942 and they referred to it as the "error-proof" dial.

How the name "California dial" came to be is debated with one interesting story stating "California Dial means fake dial […] In the 1980s when we all began this journey, whenever a dial was brown, tattered, or badly worn, we all had them refinished at a dial refinisher in California. The name of the place was Kirk Rich Dial Co."

No matter the origins, today Rolex doesn’t make the "error-proof" dial anymore but plenty of other brands do, most notably Panerai and Nomos.