I have seen this at a friend's house, they may sell it. But nobody knows what it is. The wood looks too new, but it fits tightly, and the metal looks old.
2 Photos:
http://www.hunt101.com/showphoto.php/photo/566328
http://www.hunt101.com/showphoto.php/photo/566325
2 Photos:
http://www.hunt101.com/showphoto.php/photo/566328
http://www.hunt101.com/showphoto.php/photo/566325