I can't figure out anything this could be other than a branding iron; there are gaps at either side where the hand meets the handle that make it seem unlikely that it would work as a mold or cutter of some sort. Assuming the former, I'd guess that the arm once fit inside some sort of extension, so that when hot it would not burn one's hand when using. It appears to me that it was hand forged, and is quite old (and heavy, weighing almost 2 pounds) and I just love it as an object, with terrifically snaking fingers of the hand and nice fat arm-like handle that feels great to hold.
5 1/4" long x 2 1/2" tall x 2 13/16" wide. Excellent structural condition, with some rust to the surface.