You have the rather rare 5.25" semi-bull barrel, which is nice, and a good compromise between the basic gun and the 5.5" bull barrel. A fine field pistol for small game hunting, shooting tin cans, etc.
It is worth $300 in my opinion, especially in that rare form.
Hang onto this one. It makes a splendid basic .22 pistol, and is very durable.
You will more than get your money's worth, and I seldom see them for less where I live, if in really nice condition. I would prefer your MK. II to the current MK III.
Lone Star