The "KXXXX" is the original serial #. (hopefully, for you, they all match)
This serial is attached to the date(year) at the top of the breech
on the rifle barrel. The ATF(Our paragon of virtue with firearms...
made a different serial # which is different for that particular gun, no
matter what the year. It's the long # next to KSI, Pamona, CA.
Look closely, there is probably a small 10-digit # engraved there,
which is the gun's domestic
serial# for ATF purposes.
The Chinese and Russians loved stamping their rifles with
armory markings, but due to the cold war the information
has been shrouded in secrecy for decades, and mere bits and pieces
of information from behind the iron curtain are just coming to
It looks like a great little carbine.
I hope you like it as much as I like mine.