If you’re checking a Rolex in San Diego, the reference number is engraved...
https://noon-wiki.win/index.php/Do_Box_and_Papers_Really_Increase_Rolex_Value%3F
If you’re checking a Rolex in San Diego, the reference number is engraved between the lugs at 12 o’clock, beneath the bracelet. Don’t pry the bracelet off yourself. Ask a watchmaker to check it before you sell or borrow against the watch.