The 97% MK VI (as long as it hasn't been hacked on inside anywhere) is likely going to be the best buy for a "working copy", unless you are a collector who likes the box, etc. I would stay away from the very early MK I if I were you, unless you know for sure that it was returned to the original factory and refurbished by the gunsmith. The MK VI's are stainless, not chromed, though they may have some hard chromed parts in them. The best recoil spring systems have 3 springs, not 2. The very early MK I may only have 2.