I doubt that's a bayonet because I see no mechanism for attaching it to a rifle barrel. It is an interesting knife, though. I did a very brief Google search for "S. W. Silver & Co." "Cornhill" and there is much to read there. I just gave it a quick glance, but I got the impression it's an old London company that made a variety of items roughly 150 years ago. If you read enough you may pin your knife down. Take care of that sticker and DO NOT CLEAN IT IN ANY WAY. I suspect you have something nice there. Post your pictures and questions in Mr. Bernard Levine's identification subforum and you should learn more.
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