XF 1.2 Member ID

I have a member asking what number he joined my forum. The first 100 members to join my forum were given Founding Member status and this one wants to know if he was among the first 100. I don't know how to tell that I have looked in phpmyadmin but see nothing similar to "xf_user_ID" or anything.

I realize that by having banned and deleted some members and running spam cleaner it may have change his number? Or does when a member join does his number remian the same no matter what?