a guy i work with that has a company card has the exact same cc number as me with just the last 2 numbers being different. we both have Amex spg. his is an authorized user under a business account and mine is personal. i happened to notice because i was buying something for him and the computer thought i'm entering my own cc and kept trying to finish it off and it only went away when i typed the 14th number. i then took out my physical card to compare and there it was.