Now with larger pictures..
Definaty a 1993 MAG21
MAG20 (1992) main visual difference is the lower legs are different style, different crown er different brace
Visual element that make it a 1993MAG21 (and not 1994/5/6+):
Brace : has three holes for the canti stud, you cannot really see the other difference in the pictures (you can see the chop marks on the brace in the bottom picture by the way)
Crown : Classic ring under the crown where it clamps a stanchion being the easiest.
TopCap: 1993 style, 1994 they moved to larger machined get your finger in style.
Of course all these can be jiggled with other years as can most of the internals