This little guy is supposed to be a box opening hammer. In my shop, I open very few wooden boxes. I had this little guy on a shelf and one day, I picked it up and tried to make a fine adjustment to the lateral position of a plane iron. I found it to be the perfect tool for the job. I have never been able to develop the skill to get my plane irons where they need to be with the lateral adjustment lever. This little tool works much better for me. Tiny little taps is all it takes. I think I gave 2 bucks for this at a flea market. Obviously, you gently tap the side of the iron at the top of the high side.
-- Ron in Kokomo