If you’re checking a Rolex in San Diego, the reference number is engraved...

https://brookssnewinsight.scriblorax.com/posts/how-do-i-avoid-selling-my-rolex-for-less-than-it-s-worth

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.