If you look closely at the picture of my WMP 1957 stamped drum posted in an earlier response you'll see it has the same throw off as Zenstat draws attention to above. That is the throw I'd expect to see on the drum in question. My transition badge COB Super has this same throw off and a WFL stamped butt. So that infers that the newer version of the P-83 came out sometime after the transition badge debuted.
They mount on the same hole pattern so they are easy to swap out. The earlier version seems a bit troublesome so that could be the reason it was apparently replaced on the drum in question.