Thanks for all the comments guys...they are very helpful.

A shortened barrel would explain the added front sling attachment, although you wonder why someone would go to the trouble of adding one so close to the existing through-stock barrel band. And obviously that would be easy to do with a soldered sight ramp.

Just so I'm clear: I should expect to see the serial number (or several of the last digits) in the stock inletting. If I don't find that, we're looking at a guild gun? Would you expect a guild gun to be built on a commercially-marked Mauser barreled action?