Well a little knowledge can be a dangerous (and expensive) thing... the rifle is misrepresnted and it isn't a KM rifle. Obviously an honest mistake, so it is hard to get worked up at the seller, but that buyer sure is taking it in the shorts if the expectation is that this is a KM rifle.
A very nice Danzig/1917, probably as nice as you can hope to come across, but whereas 1915-1916 Danzigs are rather difficult to find original-matching, that isn't nearly as true for 1917 production. There are more matching-original Danzig's from 1917 that all the other years combined. Which is typical of most makers, especially the heavy hitters like Danzig, as 1917 was when the rifle situation changed. Massive production in 1915-1916, coupled with a change in doctrine made the Gew.98 in less demand, just look at Amberg, they must have stored 75% of their 1917-1918 production, they are often found this nice.