I shoot weddings. I give my bride and groom proof pictures from which they select their enlargements. The proof are usually printed at Costco. In the past DSC_1234 would print on the back, and the bride would use that number to tell me they wanted additional copies of "DSC_1234."
After DAM exploration and studying the www.dpbestflow.org
website, I've decided to use something like BMyymmddxxxyyy_derivtype.ft (initials, date, job sequence, shot sequence, derivative type and finally the file type.)
Now the problem is that NONE of the places that I have used to print my proofs or prints can print a 23 character string on the back.
(This is just recently a problem. My son works at Walgreens as the photo geek. I let him print a set of proofs from a wedding, mounted them into an album, and gave them to the bride. Only after she moved out of state did I realize that there was not an identifiable picture mark on the back. She had to return to my location, and I actually shot pictures of her picture to identify those that she wanted.)