I went to the MG81/34 shop today....
I have never seen that many machine guns, crates, surplus gear in my life.
And I was amazed at how much heavier the guns were than I imagined.
Saw a huge crate of bakelite butts, flash hiders, ...bewildering amount of stuff.
Now heres the thing....none of the guys at the shop could figure out what the hell the solo piece was.....all of them came over, tossed around ideas (which I figure amounts to as at least 75 years of collective knowledge among them).
Not a one could figure out what it where it came from. Although a few ideas kept popping up.
1] it was an asian made piece or eastern european piece with very little reference for us to go on in the west
2] it was an extremely small experimental run--There were apparently a zillion modified parts for these guns.
3] or it was a combination of two parts, base and cone
I did learn why those small U shaped notches existed. The piece threads on. Apparently as it rotated the flash hider could be locked into position much like a sterling butt cap locks on. To lock it in place, a lock arm piece clipped down into the U shaped notch. The reason it would be rotated up or down was to effectively deal with the flash and gas, depending on the use of the gun. Interesting.