Tried this over at whatisthisthing but didn’t get a lot of traction. Hoping you guys can help!
This was my grandfather's knife and the family story was always that he brought it home after taking it from a dead German solider, one way or another.
The tag is pretty withered away, but you can sort of make out his rank and first name as well as the letters “ASN”
Album below. Definitely a British penny on the bottom, but not sure if it was tack welded there after the fact or what.
No name on the blade, not even Solingen ? Looks like it's either been cobbled together, or been repaired. Maybe someone had access to an old blade, or ground one out of a wagon leaf spring, put it together. Or, maybe he had found the knife, but the haft came off. He then quickly whittled and drilled a new one , wrapped it with a thong, mounted it on the tang, drilled a penny and ran the tang of the knife through the hole, then either soldered or hit it with an oxyacetylene torch to puddle the tang down around the top of the penny ( depends on what that lump is, solder or welded steel).
Some good cleaning of the blade might indicate whether the same clumsy hand crudely ground it from a spring as well as fabricated the rough handle. If the blade is a well-tapered, flat, carefully ground one, they likely found a factory-made blade or knife and put a handle on it.
This would not be the first time a family put two statements of fact together to make one erroneous tradition, so: 1) Grandfather was in the War and got a knife off a German 2) after Grandfather died, we found this knife among his things THEREFORE this was the knife grandfather got off a German solider.
Have you also tried r/knives or r/knifeclub? Lots of knowledge over there. They'll also have good advice for how to take care of it.