Someone on another forum saw your pictures and speculated it might be from a 1914 Revelli machinegun. But he needs the dimensions of the bolt face opening to see if it would accomodate the 6,5X52 Italian cartridge head. Measurement needed. Edit- Maybe it is called the Fiat-Revelli. There was also a 1934 version that I believe was chambered for 8MM ammo. The photos I have seen online are not too clear and thus I cannot identify the bolt itself with certainty but may be Italian.