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[Sevens]

What is this does anyone know? I know that it is scratched into the back of it with a capital A and a capital I think it's a B then on the bottom it says 4

 

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[Blackfoot58]

What is this does anyone know? I know that it is scratched into the back of it with a capital A and a capital I think it's a B then on the bottom it says 4

It kind of resembles the female half of a latch. I’ve seen window latches that were similar, but this one may not be.