P08 byf 41 with disc on right grip....???

I've been discussing with VIS35 about the above that I picked up at a local show. It is all matching #92xxa with all waffenampts intact and obviously a rebuild from Russia or E.Germany. But unusual with all waffenampts intact and all matching. It has an extruded magazine with plastic bottom and the most unusual of all, it has a metal disc in the middle of the right grip. There are no markings on it, but it looks kinda like a washer without a hole. It has a center screw rather than two across from each other. The significance for the disc is up for debate..any help would be appreciated.


Thanks,

Ol'Duke