they're NOT rare- when you could get the norinco ak-47s, you could also get the so -called "big brother) ie the rpk for the same money- about all that amounted to was a longer barrel, 40 round mag and bipod for maybe another 50-100 bucks- the reason you don't see a lot of them around is that 1) they're an ak derivative ( as far as the c-68 is concerned( probably named, but don't quote me on that) and when you picked that up compared to the ak, the rpk was big, clumsy, and showed stupid in the hand- so the average joe left the rpk there and bought the ak and bought 40 round mags for the ak- and there was something like 10x for every rpk imported- now, they're all prohibs, so it's a moot point anyway- oh, yea, and the one i did shoulder was a 223 version, with the skeletonized buttstock
and it's a RUSSIAN design, meant to replace the rpd- the chinese( ie norinco) simply copied it