Thanks for all the replies!

Pappa has hit on a naive question I have: will 8x57 Mouser even chamber in an unaltered 8x56 M-S breech? (The answer seems to be 'No' unless I used a hammer.)

Having said that, I have loaded Pachmayer anodized aluminum snap caps in 8mm Mouser into the rifle and found no scratches or marks on the snapcap after ejecting from the breech. If 8x57 Mauser would require pressure to chamber, then I would expect to see marks on the snap caps.

Igorrock, I am speculating that it is the longer action rifle, do not know it for certain. I hope I did not mislead you. I got that idea from a fact sheet from the Mannlicher Collectors Association, assuming that it was 8x57 of some kind, so if it is 8x56 M-S, then the 1908 identification is on target.

Thanks all!