I dont know the really caliber/cartridge, just said that an 22 lr fits the chamber perfect.
I know the timeframe for the .22 and still looking for an answer since when the .22 lr was made in
germany based on an printed source .
I will cast the chamber to get exact measurements. But it is not easy to find datas for the 6mm Flobert,
found around 4-5 different datas in the www.......
Rifle has no proofmarks, sn comes later because i dont have it by the hand right now.