Both of your bubblebacks, Abel, are great, but the 3131 (and matching bracelet) is really extraordinary.
I agree that the dial on your steel bb is refinished, but nicely so. An original Roman-Arabic dial should have the numerals stamped into the metal of the dial (you can tell with magnification) so that extra lume could be placed in the spaces. Also, original lume can be recognized with close inspection with a loupe, the fluffy, grainy consistency.
e.g. this close-up of one of mine. You can also tell how the numerals are stamped into the dial on this "Semi-California" dial.
It is a matter of some debate how the popularly-known "California" dial got its name. One somewhat far-fectched explanation I've read is that some vintage dealers (supposedly in California) way back at least 20 years ago brought this distinctive style to the attention of collectors, and made the originals so coveted, that they popularized redials in this style.