We thought it rather nice that the guards in a slave labor camp allowed the prisoners to keep their jewelry.  Actually, the ring Bill is wearing is a family heirloom which, at the time of this filming, he couldn't get off.  It's turned around so the diamond doesn't show.  Keep a close eye out and you'll see it in all of Bill's films until his cameo in Maverick.  He had it cut off before filming began.  We miss it.