I have a Trooper MK III with a vented MK V barrel. The barrel is stamped " Trooper MK III". It is blue with a four inch barrel.Serial number 310xxU. Does anyone know if this is an oddity or were many made this way?
When Colt was changing to the Mark V design there were some late production Mark III's fitted with Mark V type vented barrels.
Apparently there were also a few Mark V's fitted with un-vented Mark III barrels.
At Colt odd things happen during changes to models.
Your vented Mark III is not common but not extremely rare.
I saw a MK III Trooper barrel on a MK V frame (and MK V pony) not too long ago - the mismatch caught my attention as I always notice the MK V Ponies with the "V" in it.
Anyway, this gun had been treated really bad, kind of like it was an illegitimate stepchild. Whomever owned it sure mistreated it -- on the other hand, the dealer's table looked like a real scrap pile.