The "California dial" is a distinctive style of watch dial that combines Roman and Arabic numerals, usually featuring Roman numerals at the top half and Arabic numerals at the bottom half of the dial. 

This design typically has Roman numerals from I to XII at the top half of the dial and Arabic numerals from 1 to 11 at the bottom half, with a triangle or inverted triangle at the 12 o'clock position.

The  California dial is a sought-after variant among collectors, especially on vintage Rolex watches. These dials are known for their unique and eclectic style, blending different numeral styles to create a distinctive aesthetic. Rolex has produced watches with California dials in the past, particularly during the mid-20th century, adding to their allure among enthusiasts.