Show us your ball butt.... pistol

[qusko]

Dear forum members,

I've bought attached balkan ball butt pistol. Do you know how barrel was attached to the stock? There is no place for a pin and it is only fixed by the screw on top of the lock.

Example I have was with a band, but for me it looks like not original one (replacement). In some other examples I saw silver wire, but it also looks like a temporary solution (even though .. maybe from the past)