Wow great guesses! My first guess when I glanced it was a punch, easy guess, because it was in a box full of chisels, punches, and other items... Then the reality of physics took over and I got a Zonk on that guess. I never thought of the cotter pin puller, I like that one... It does make a good back scratcher.
If you don't want to wait until this weekend you can always look it up on a Plomb catalogue 1939 and most of the 1940's. Just don't say what it is..
Thanks..