The best thing about this topic is that it can never really be answered. And exploring all the theories makes for interesting observations.
Personally, I don't believe that the different stars on the receivers correspond to the date change of the flag. It makes zero sense for that point in time. The flag change was 54 into 55. The Chinese weren't even making the SKS in 54, and they were just learning to make them in 55 and not into their own full production till 56. So why would the Chinese be making another country their own SKS, when they themselves are just starting to learn to make it? Makes no sense.
I think people may be looking too much into the star differences. Remember what I said earlier.... the North Korean guns have a fat star stamp on their stocks, and they NEVER used a fat star for anything.
Now I've seen people mention that the Chinese switched to short lug in 65, so why are the "65" NVAs long lug if they were built in 65?
Well, think about it.... There's only a couple thousand estimated NVAs for each year. Jianshe is switching to short lug barrels, but still have a few thousand longs left. Wouldn't it make sense to use them up on a gun you're making for someone else?
Just some food for thought