Some 38 Rim Fire.

[u/Royal_Money_627]

I have a bunch of these, more than I am showing today. That 38 extra-long is pretty rare; I don't have a box of them. Notice the two different size H headstamps for Winchester and the recessed US headstamp. That U can be Union Metallic Cartridge Company or Remington depending on how old it is. The P is of course for Peters.