When I was young, limber and could jump a three rail fence, I used to shoot revolvers with some Border Patrolmen. From time to time I got to shoot their "service revolver", which at the time was a special order Colt Official Police with a straight no-taper 4 inch barrel. Colt ordered 500 of these in 1954 and they are marked as in the pic below.
I really liked the way these pistols handled, balanced and shot and shooting them is probably what made a lifetime Colt fan out of me.
Much later Wilson in his book on Colts said these were built on Police Positive frames. I knew they were not and wrote him about it. I got a pretty snotty reply along the line of who was I to challenge the nation's foremost firearms expert on matters like this.
At the time, I was making frequent trips to El Paso and visited the Border Patrol museum and sure enough they had a number of these heavy barrel OPs. When they were phased out, the Patrolman to whom they were issued could buy them and some of the folks had donated them to the museum. The curator allowed me to handle them, write down their serial numbers and take a photo. Back home I contacted the INS historian and after a search, she sent me a copy of the original contract with Colt. Sure enough they were Official Police models.
I wrote Wilson again, but got no reply. About this time, he was having some serious legal issues that took him out of the expert business.
I have never seen one of these Colt Border Patrol models come up for sale, but the heavy barrel Smith and Wesson Model 10 served me just fine. I do have a friend that has a new barrel for one of these, but he isn't parting with it.