Hat badge for something. Whether British or Canadian I don't know. I can't find a 43rd badge like it. For the life of me I can't figure out/read what is above the 43.
Perhaps "CG". If found on this side of the "pond" I would put it as an 1812 or later shako plate. It's a nice piece. Note: The British 43'd foot was in Canada 1836 to about 1846. Their badge was different from this one, however.