Okay, here's the sight photos from the seller. The only thing I can say definitively is that me & this rifle will be spending some quality time with a bottle of Kroil.

But to my uneducated eye this looks like 1) a bona fide commercial Mauser; 2) a square bridge action; and 3) a windage adjustable tangent sight is installed. Tonight I noticed a very similar sight in Speed's sporting rifles book that I overlooked before; check out the Kurz action on page 96, plate #156.