There is no Colt Mark II.
I've always wondered about that, but I don't know why Colt went from the original Trooper to the Mark III Trooper.
Depending on actual condition, $375 is a very fair price for a Mark III 8" inch .22LR.
The .22LR Mark III's were lower production guns, and due to the unpopularity of the 8" inch barrel, it's a very low production model.
It should shoot with a high degree of accuracy.