To the best of my knowledge, only the slide, frame, and mags. As for value, lately the prices have been going up and the supply well is running dry. The value is really determined by how much an individual is willing to pay. I have seen Maks go for $150-$900 lately. It all depends and is relative. Maybe not the answer that you're looking for, but, an answer none the less.
All the East German Maks that I have seen have the last two digits of the ser.# electropenciled on many smaller parts of the gun.
Whether they are all that way I don't know.
If frame and slide ser.# are mismatched value would be diminished. To what extent? Depends on the buyer, shooter or collector?