On another forum there is a thread going about Mauser military rifles produced by Steyr, Austria. The discussion centers on the +/- # stamps found on receivers and barrels. It seems that the two may be matched by corresponding + and - numbers. As an example, a barrel may have a +2 stamped on the barrel opposite the rear sight and the receiver will have -2 stamped on it. The numbers seem to run from 1-5.

My question is: could it represent a method of barrel fitting? If yes, could it be they were able to index thread so that they could control the position that threads started in relation to achieving a TDC/sights and proper headspace? Then when assembling rifles, matching corresponding +'s and -'s resulted in reduced fitting time. Orrrr, do you think it is something else?

Something else. I have never seen a Mauser with indexed threads and there is no reason to do so. Spare barrels are not supplied with sights. And the safety breech ones are not cut for the extractor.

TDC of the sights/bands was achieved when the sights were soldered onto the barreled receiver AFTER the headspace of the barrel to reciever had been qualified.