Can you provide a photo of the bottom and close-ups of the markings? That would be a big help.

Is the tray metal or ceramic?

The perimeter of the tray has flutes sized for cigarettes, but it is a big ash tray. At approximately 14: x 10", it could handle a big cigar. Do you know if this tray was intended for use by a sizeable number of smokers such as a hotel lobby or the sitting room jn a men's club?

says California pottery was in business til 1929.. i'd guess the ash tray comes from the 20's era.

Here is a link that might be useful: wiki for california pottery

It was not all that uncommon for quite large ashtrays to be used in the home, and many of the art potteries made them. I have a couple whomping huge weller ones.