The MK-V was designed to lower Colt's costs. The finish and machining were not near as nice, and I believe it was the first Colt to come with rubber grips instead of wood. They were made in 4 & 6" barrels, but I never saw a 4". I had a MK III and a Python, while a buddy of mine had the MK V; you could REALLY tell the difference when shooting! While most all of Colt's revolvers shared the same lock work, the later models were not nearly as polished. It was a sad decline to watch.

The difference was the MK-V was a total redesigned revolver form the MK-III. Nothing was interchageable. The MK-V was only made for a couple of years I think.

MkIII and MkV are very similar and neither has the Python style action. Frame grip shape, shorter action, and cast hammer and trigger are the only big differances between III and V.

To the best of my knowledge ther are three different troopers. The first was made until 1969 and many refer to it as the poor man's python, The guy who sold it to you may have confused the mark V with this. The Mark three was a complete redesign with no interchangeable parts with the original. From 82-85 colt produced the Mark V again a complete redesign.