Indeed...
The information below us paraphrased from the book "The SKS Carbine" by Steve Kehaya and Joe Poyer, 4th edition, North Cape Publications.
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Factory 26 = state owned and the oldest arsenal in china being established before ww2. Located in the city of chongqing. The civilian name of the factory is jianshe machine tool factory. Factory 26 is believed to have produced as much as 60% of all Chinese SKS.
Factory 316 = located in yurhe, zhejang province and established in 1965 primarily for SKS production. The factory was moved to wukang in 1995.
Factory 36 = located near longyan, the factory covers 20 acres and 30 buildings. The factory director claimed to have shipped 250,000 sks in 1993/94 to the US. The factory closed in 2002.
Factory 66 = located in Bei'an. Started production in the 60s. Was still producing arms until 2008 when the factory was heavily damaged in a quake.
Factory 96 = located at Xiangfan, it's stamp was 416 in a triangle unlike the others above which used their actual number. The factory opened in 65/66. In 1987 the factory was still manufacturing the sks for export and the PLA which contradicts the notion that SKS production in china for the military ceased in 1980. Witnessed by Poyer/Kehaya.
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Like I said, if one had the right visit, and asked the right questions, I'm sure a lot could be learned. Marstar has claimed to have a lot of info in their archives, but not the time to go digging for a history lesson.