Officer's Model Target 456439 was made in 1920.
If it was the later Officer's Model Special it would have been made in 1950.
The Officer's Model Special was Colt's early post war Officer's Model made from 1947 to 1951.
It had the Colt Matchmaster sight used only on that model and a fat, untapered super heavy barrel.
Colt had the aggravating habit of mixing some models serial numbers in with other models. Your gun's numbers were mixed in with the Army Special.
In any case, based on the serial number you have a 1920 Officer's Model Target.
As to the patent dates on the barrel, this would be explained by an old re-barrel job, which was not unusual.
From the beginning in the 1840's up until the mid-1960's all Colt firearms started at serial number 1.
This means you could have literally a dozen or more Colt pistols all with the same serial number.
In order to ID a specific model, you have to go by frame size and the barrel markings.
The problem is, most Colt revolver barrels could be interchanged with a number of other models.
This can make identification difficult if a revolver has been re-barreled.
This often causes confusion when you have a gun with a barrel that says one thing, but a serial number that doesn't agree.