It would have been rare, but not unheard of, for a Combat Master in the 4-thousands to have a two piece barrel. The employees at the factory were allowed to purchase parts for cost. They often put together their own concoctions and sold them to supplement their incomes. (In some cases, the less honest ones stole the parts, and then, any combination of parts was possible).
A few might even have Colt National Match barrels. All too often, the "less honorable" employees would call the throw-together guns 'collectors items' in order to get more money for them. I know of Detonics collectors who got taken to the cleaners on some of those.
A true Detonics, with a low serial number, will be of greater value than a later one.