Never seen anything quite like this. I'm not sure it is a woodworking tool, wondering if it might be for mining.
http://cgi.ebay.co.uk/VINTAGE-ANTIQUE-WOODWORKING-ADZE-/260766090551?pt=LH_DefaultDomain_0&hash=item3cb6dec537
http://cgi.ebay.co.uk/VINTAGE-ANTIQUE-WOODWORKING-ADZE-/260766090551?pt=LH_DefaultDomain_0&hash=item3cb6dec537