Colt Trooper is an early model, it dates to 1966 All the original Troopers were made without an ejector rod shroud. It has a six inch barrel. I especially like the caliber marking .357
Yours is a 1966 Trooper. Early Troopers were .38 Special, later in .357. They are nearly identical to the 1950s 3-5-7, the immediate predecessor to the Python. Basically, yours IS a Python, except for the barrel style. The idea was much the same as the S&W Highway Patrolman. A less expensive and lower finish quality version of a top-of-the-line model for use by law enforcement. I have both a 3-5-7 and a .357 Trooper. There is very little discernible difference. It has the firing pin in the frame, not on the hammer. Not sure about the originality of the grips. Medallions should be silver, not gold. But they are Gen 3 target grips and are period correct. Take a close look to see if they might be substitute medallions. Only Pythons left the factory with gold medallion grips. Medallion substitution was not unusual. Many troopers shipped with service grips but could be ordered with target grips as an option. My Trooper was shipped with service grips and I later found a pair of Gen 3 targets for it. Troopers are excellent revolvers and are very desirable Colts. And somewhat less expensive than Pythons for no good reason.