Crank for a window made in 1957

That is one old operator. We carry a few that have a similarly designed base, such as our 39-001 and 39-002. However I don't know if the arms match up to what you have now. Start with these two, at least, and try your best to remove your operator from the window. Then you can compare the size and style of the arm to our products. If it differs, you can show me a couple more photos and we can work from there.