Its Remington Brass. The R-P is for "Remington Peters". I have not used their match brass before. I have tuned up some of their common fodder and had good results.
do you have a ball-mic? If so would you mine taking multiple readings of the case neck thicknesses on a few pieces? I'm curious as to how it compares to regular Rem brass. Thanks, man.
I've fired 17 or so from one of my Dad's boxes--it's packed in 1960s vintage green boxes and is marked 7.62 Match or something like that. Loaded with early Sierra 168 SMKs, think they were still called "International Match" back then.
Then again maybe I'll keep 'em for a full lot of 100...