That gun has so many confusing and contradictory marks that I am just confused. They just don't make sense.
It started out as a standard Gew. 98, in or before WWI. Probably after that war, it entered civilian life and appears to have been converted to some 10.?mm cartridge, since the barrel shoulder is marked to show a bore diameter of 10.2mm. It underwent commercial proof apparently with a steel jacket bullet of 157 grain (10,2 grams) bullet, which is not consistent with the 10.2mm bore. Then there are Weimar-era military eagles all over, stamped at random, plus the normal original inspection markings (one almost obliterated) on the right side of the receiver.
Then there is a number on the barrel that doesn't match anything, though the barrel serial number looks original.
Then we have the Totenkopf and the "SS" marking. And the original receiver markings on the top have been removed.
At some point, the barrel was shortened (or replaced), the bolt handle was turned down and the sights and stock replaced with those of K.98k configuration.
The first thing I would check is the actual caliber. After that, I would love to hear other ideas.
Jim