How old? Too old to consider it a shooter, more than likely. Probably post-1900 but pre-1940.
Value? To you, priceless. To anyone else, it's a shotgun-like object most likely suitable only for decorative use. Single-shot wallhangers don't bring a lot.
Make? It's what's known in some circles as a 'hardware store gun.' IOW, not a big-name manufacturer.
The buttplate is a replacement, not original to the gun.