From the photo, this is a M1903 Turk Mauser action, reworked, remarked and rebarreled to 8x57S in 1932 by the Ankara arsenal. Evidence: the cutout in the rear of the receiver ring to allow passage of the longer, compared to a 7.65x53 cartridge, 8x57S. 88MauSporter is right: This is a "Intermediate length" action, same as the 1909 Peruvian (NOT Argentine!) or the commercial actions Mauser used for the Rigbys and other rifles in 7x57 aka .275 Rigby. The bolt and it's travel is about 5mm/.2" shorter than the "standard length" (Gew98, K98, Argentine 1909)action. As the standard length action properly opened up to take the .375 H&H Magnum is marginal in length, opening up this intermediate action is impossible or ridiculous! Perhaps this is the reason the barreled receiver was offered cheaply. You even cannot fit the barrel to a standard length action, as it's threaded shank is too long and too small in diameter! It will be rather difficult to find a proper intermediate bolt assembly and bottom metal. If the barrel is already chambered for the .375 H&H, you have aquired an expensive piece of junk! If you are lucky and the barrel is still without a chamber, it may be chambered perhaps for one of the shorter .375" cartridges.