So I'm going to act as more of a guiding force than as a definitive answer here because the answer is "I don't know." I collaborated with a friend of mine who has an amazingly large amount of knowledge of Germany in WWII and firstly we both confidently agree that this is a German bayonet. We know that much, the style fits. Beyond that it's getting to a bit of a crap shoot. I used this bayonet identification guide to compare it to WWI and WWII bayonets. With that we can confidently say that it is, by all likelihood, a M1884/98 Mauser bayonet. Now it's either a II model (used in WWI) or a III model (used in WWII). Honestly I can't know for sure with the pictures provided and probably wouldn't be able to tell without having physical copies in front of me to physically manipulate. However my gut tells me that it's WWI as German bayonets in WWII did not have such a pronounced quillon's.

As for the markings it's likely a battalion stamp. It would help if we could narrow down what war this was used on or even where it was used in some general sense but the phrase I'm making out is "2.LNK.E". The "2" means it's "2nd" something, "K" means "Kompanie" and the "E" I would wager means engineer. I don't know what "LN" stands for immediately.

TL;DR: Certainly German. Has qualities that fit both a WWI and WWII bayoent (ie: smooth grip & construction quality demonstrates WWII but prominent quillon demonstrates WWI). Honestly can't tell from the pictures. Those golden rivets also confuse me. If I was pressed and had to look at this picture without context I would guess this was a WWI bayonet that underwent modification from a collector.