Binko:
I can't tell without a pic of the top tang, but it looks similar to a Treff, Collath or Meffert underlever or Roux breech. It has 65mm choked 16 bore scattergun pattern welded tubes with some variant of the 360 BPE allowed in the rifle chamber, which looks to be cast steel. The 118/35 means the 108/49 - 0.350" plug gauge wouldn't enter and the 0.340" plug would pass the whole length. Without a chamber cast, I would venture a guess of 360 2 1/4" Express(9.3X57) or 9.3X72R.
Kind Regards,
Raimey
rse
