this will be the german form of the 450 BPE

possible 11,5x60R 450
11,5x65R 450
11,5x82R 450

all Blackpowder or Nitro for Black rounds, making in germany and austria till WW 2.

notice: chamber dimensions from many of this old guns follow the old coiled case very close and will not fit the later british form without resizing