If you’re checking a Rolex before selling or borrowing against it, the...
https://www.third-bookmarks.win/if-you-re-checking-a-rolex-in-san-diego-the-reference-number-is-between-the
If you’re checking a Rolex before selling or borrowing against it, the reference number is engraved between the lugs at 12 o’clock, under the bracelet. Don’t pry it off yourself. Have a watchmaker or reputable buyer inspect it and document the watch.