All About Pocket Knives

I recently inherited a reasonable collection of daggers and folding knives amongst the collection are quite a few variants of the world war II British jackknife in varying States I have resisted the temptation of polishing the blades etc as I did not know whether this would harm there collectibility also the dagger I have posted if anybody could identify it I would appreciate it at first I thought it a world war two Japanese paratroopers and boot knife but I am not so sure also as it has a blackened blade can anybody give me any care instructions for the piece thanks in advance

I'd cleanup the marlin spike sailors/yatch knife, they aren't particularly rare or valuable so you may as well have a little fun with it. I'll leave advice on the dagger to others more in the know.