7,62 Russsian headstamp markings?

This may have been discussed before, but I couldn’t locate.

These images of a USCCo. 7,62 where sent to me by member treshkin.

Anyone have a guess about the circular pattern around the primer ?


Edit: Apologies to Mechanik,any omission was unintentional.

As we can see, the author of the top picture and an owner of the cartridge is member Mechanik