What do I have?

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I bought this rifle from a pawnshop a while back and can find no markings on it anywhere. It looked like there is an adjustment screw missing from the rear sight and I need to order parts. I bought some Fenix 22 cal. pellets for it and they are too big so I’m thinking maybe a .177 cal. This is the first air rifle I’ve owned since a was a kid in the early 70’s and got one for Christmas. I was hoping the experts here could help me figure out a brand and possibly a caliber. 
 
They were $20 and if yours has an oversized 177 barrel that don't seem to like anything you shoot then try the OVERSIZED 7.9gr (specifically the 7.9gr) Crosman Premier SUPERPOINTS that shoot terrible in most other normal 177 guns since they are way too oversized.

I went through A LOT of them B3 rifles over the years b4 getting a real freak of nature unbelievably accurate one that I am keeping.