It may be a Glascow mark The lion Rampant, in particular the shield design appears to be right on. The C would be a date letter with the specific shield design indicating which year also, because letters have been used as date codes for a couple hundred years at least. The shield design is what changes along with the font itself. Then again it could be an American mark. It's definitely not a Gorham mark, though there were others that mimicked the British marks as previously mentioned.