What's this?

A torture aid?

Answer: Hook knife for picking ice. Before the advent of refrigerators and freezers in households, there was an entire ice trading industry. It was harvested in winter, collected from the surface of reservoirs, and then placed in special glaciers, where it could be stored all year round and from where it was delivered to customers at home in the form of blocks. The hook that you see in the photo served both to break off the ice from the block and to move its pieces without touching them with your hands.