Help needed identifying bayonet ... thanks

[KAL]

I just inherited an old bayonet that has been in the family as long as I can remember. My father always said was from the US Civil War ... but the only mark I can find is a "Y" at the base of the blade. I've done a little research, and I assume it's a socket bayonet, but I'm puzzled by the "Y" mark (British Yeoman?) It measures 20 1/4" end to end, blade is 17 1/16" and a penny can fit in the socket which is 3" in length.

Thanks,

-Kevin

[Anderson]

I'm thinking a British Pattern 1853 Enfield bayonet. The "Y" could be Yeomanry, which would explain no Board of Ordinance mark.

[KAL]

Thanks!