My father in law was an American History buff and when he passed away, I inherited this Civil War Bayonet: http://imgur.com/a/B9qrs To the best of my knowledge, it has not been acquired illegally or is otherwise illegal to own.
I'm really interested in learning as much as I can about it as I get a lot of questions on it when I have friends or guests over. There are a number of numbers, letters, and symbols and while some of them match up with some information I've found, a lot of them do not. I know bayonets are fairly common, but I just wanted to know about mine.
Any help you guys can offer is most appreciated.
That appears to be an 1876 pattern Martini Henry bayonet (especially the scabbard). The blade markings indicate it was made in Britain (the broad arrow and W.D.). The crown over the E and 27 is the inspectors mark. The 1 over the 77 indicates it was accepted in January 1877.
A quick way to tell is to determine the length. 1876 patterns had a blade length of about 22 inches in length, an inside socket diameter of about .72 inches and a socket length of about 3 inches.
You might also try r/whatisthisthing.
There are a lot of people with niche knowledge there.