The bayonet is a very dull/matte dark grey.. not true dull chrome looking silver like the rest. Almost looks like it was sandblasted.
I haven't seen many stocks sanded....unless bubba did it. Serials should be pretty clear, if faint or non existent... Someone may have sanded it here.
What I've seen, M59s will carry about a 100 to a 200 premium over the M59/66, over all condition carries some weight.
Study the picture of my orginial post to see the M59 gas block, the M59/66 is totally different, the M59 is more kind of like a later Russian or earlier Chinese.
In my opinion...your over complicating the serial numbers. Nerither of mine really have matching numbers...most parts just have the assembly numbers. The bolt and carrier have serial numbers and I think, one magazine. Do not expect to find serials stamped on every piece. If mismatched....they still hold value, maybe a handfull match, largely because they have been rebuilt who knows how many times. Remember, Yugoslavia actually used these, they didn't just make them like other nations to collect dust and sell years later.
Yes.. you can find different shade of blueing, one of mine has a purpleish tint, not the normal deep dark blue. I've seen several, totally normal in my book.