Part is 3 inches by 1/2 inch and the only marking is a R I believe to indicate right. The material is plastic and has a spring on the back side
Bob from SWISCO responded:
June 11, 2020
These old storm window latches can be hard to come by, and dimensions have to be precise. Yours remind me of the 91-054, but the dimensions you cite don't match up, so I'd double-check to see. You can view the rest of our storm window latches here.