I've seen them marked M model and D model. Also seen them with
a non thumbhole stock--but only a few.
Price. I've seen them in good condition with asking prices from $250
all the way up to $700+. 300-400 is probably where most of them are.
Neat little gun--typical Norinco crude finish and it goes bang with every pull
of the trigger. AK mags are cheap and plentiful, and much better than
any hi-cap duckbill mag.
I've had one for 17 years or so, actually used it in a few 3 gun matches.
FWIW, about 4 30 rd mags run through FAST will turn the barrel gray and
the top handguard will burst into flames.