I thought wrench but why would it have a stop collar on it and be so small. Is a buggy wrench that small. I've never seen one but it was found near what was a very popular river ford and the site a revolutionary war skirmish.
Miniature oar lock? No, I suppose not. But my guess would be that rather than a wooden handle you needed an extension bar that slid over the existing handle, as that short handle wouldn't give you the leverage you need for a rusty 1" nut.