Bayonet is fixed to the lug by a screw and a spring pushing on the body keeps it locked.
It's Russian, like you caught it's Cyrillic on the serial number.
Also the Tula factory mark should tell you as well.
It's Russian.
I like the spike bayonets just because it reminds me of the Mosin Nagant bayonets, that and they can double as a nice screwdriver.
Thinking about selling my Yugo SKS.
