Beautiful gun 7.62. You don't see Izhevsks in that condition often, very nice indeed.
Proofs should be on the side of the barrel lug. I've typically seen a (o) on the left, often a (K) on the right lug. There are often many other stamps though. Truth is, nobody knows the detailed history of these proof marks, whether they remained constant transitioning from Mosin->SVT->SKS, whether they stayed consistent throughout SKS production from '48 to '58 & Tula to Izhevsk, and whether they were consistently applied to the same part of the rifle in all cases.
The S/N restamp was how CAI decided they wanted to translate the Cyrillic into Roman font. To be honest, they are probably the most desirable of the big 4 importers with regard to import stamps from the '92-94 import window.