Do you have one? They produced about 38,000 of them in 8 X 57, but they also made about 125,000 in 30/06 for various countries, 8,000 in 7 X 57 for Venezuala and over 5,000 of them in 7.65 for Argentina. If you own one it is probably 8 X 57, but make sure before you stuff anything in it.
I have never shot one, but was at the ronge many years ago when my grandfather fired one after reparing it. Functioned well and shot ok, accuracy-wise.