https://www.gunbroker.com/item/922596974

This is an interesting one. Very nice lines to my eye and a Lyman 35 sight. Looks like it has been well used and also abused. The Mauser numbers appear to match and the action dates to about 1911.

The seller says the caliber is 7x57 but the markings on the barrel are confusing.

The Poldi Anticorro markings seem to indicate stainless steel ("SS") and perhaps the "No 754" is the Poldi barrel number? The profile image of a lady I think is the Poldi trademark.

The markings underneath the barrel make no sense to me. "6,3 mm" and "53 1/2". I know of no caliber with a groove or lands diameter of 6.3 mm. Perhaps this is a rounding of 6.35 mm which would be .25 caliber. If so, I don't know of any .25 caliber cartridges with a case length of 53 1/2 mm. Or maybe the 6,3 should be 6,5. In that case the 6.5x53R cartridge might be a fit as the cartridge length is 53.5 mm.

Then there are the gouges in the inletting. The stock number seems to match the Mauser number. But why would someone gouge out these big chunks? To fit a different barreled action to the stock?

Anyway very interesting. I hope some of our real Mauser experts have some insights.