It looks like factory 946. The best place is probably military surplus collectors forum. They have a very good thread on dating them.
I posted on the SKS forum and was told it is factory 946, dated 1968.
I found this added info on the SKS forum:
-These guns have all been new recent Canadian imports, I know of none in the US beyond the rumor of one from a pre '92 import.
-Most have been in exceptional condition.
-They all have the right side stock circle star stamp (on original stocks)
-Stocks all appear to be side swivels.
-Configuration appears to be short lug barrels, late bolt carriers, late FSB, milled trigger groups, one piece gas tubes, numeral 3 RSL, & spike bayos. Likely were utilizing a mix of new and older hardware as by year 15 at /26\ some of these features had long since changed.
-They range from year 13 to year 15, seven digit S/N on the receiver, 5 digit S/N's on the stamped hardware.
-The incrementing S/N is low (in the <5000 range, indicating this was a small, low scale production site as compared to the big boys of /26\, /416\, or /636\.
