I agree, I think it's early firearms related, but if so, in a very narrow manner, perhaps a decoration on an Indian Trade Musket. The way it's made, a pin must pass through the stock to hold it in place. That means it can't be placed along the bottom of the fore stock, because it would plug up the ram rod hole. That means the only place that I can figure is perhaps on the wrist, and those are usually nailed on. Here are some photos to show what I mean.

This is a pistol showing a thumb piece, note that it's nailed on.

These are ram rod pipes and an entry thimble. The ramrod pipes fit in the groove from the muzzle down to the entry thimble, where the ramrod enters the wood.

This is the inlet for the ramrod entry thimble. Note the slot for the flange.

The hole is drilled through the wood and the thimble. Note where the ramrod enters the wood. When the thimble is in place, the pin goes between the barrel and the ramrod.

This is a picture of a ramrod pipe being drilled, again the pin is between the barrel and the bottom of the groove for the ramrod.

The trigger guard is also pinned to the stock. The ramrod hole ends at that front flange on the trigger guard. So there is no place between the muzzle and the rear end of the lock for your find to be pinned to the gun, that just leaves the wrist, so to me, and I'm making an educated guess, a swag, it's off an Indian Trade musket as a wrist decoration, and I say that only able to back it up by saying it just looks like it would be on a trade gun. If it isn't the front part of a trigger guard, then in my experience I've never seen anything like it on a long rifle. Perhaps a musket or fowler, probably a trade musket.