There is what appears to be a Colt Model 3-5-7 being advertised as a "1954 Colt Trooper 357" on the EE right now....from my Colt books and the site
www.coltfever.com the Trooper was only available in .38spl until the early 1960's. Either it's the wrong gun or the seller has the gun dated wrong.
The gun was listed a few weeks ago and i did send a PM pointing this out. Not sure if I wasn't clear but I got back a PM insisting it was .357magnum and offering to email me more photos.
It's been relisted today along with a Police Positive.
From the coltfever website......
"In the early 1950's Colt began to update their product line with upgraded revolvers.
Colt realized that the gun buyer now wanted double action revolvers to have adjustable sights so they offered two new models with the desired feature.
These were the 357 Model and the Trooper.
The Trooper was intended to be sold to law enforcement and civilians wanting a less expensive adjustable sighted revolver, with the 357 model for sale to those wanting the .357 Magnum cartridge or wanting a higher quality revolver.
The new Trooper model was really nothing more than the Colt Officer's Model Match with a ramped front sight on a large ramp base.
The Frame was Colt's standard medium size "E" frame that had been made virtually unchanged since 1908. The only real change was to thicken the top strap to allow extra metal so an adjustable rear sight could be installed.
The new revolver was introduced in 1953 and was an immediate success with law enforcement and civilian shooters.
Offered in .38 Special, Colt also introduced a .22LR version for use as a "trainer" gun to complement the .38 Special version.
The Trooper sold well, but the 357 sales were less than expected due to the introduction in 1955 of the super-premium Python. The Trooper continued to sell well to law enforcement and civilians, but those wanting the .357 Magnum cartridge and a higher quality gun were buying the Python.
With sales of the 357 down, Colt decided to simplify the line in 1961 by discontinuing the 357 and offering the Trooper in .357 Magnum as well as .38 Special.
The original Trooper had been made on the "E" frame which had the firing pin mounted on the hammer. The 357 and Python used the new "I" frame which was basically the "E" frame only with the firing pin mounted in the frame.
What Colt actually did was to switch the Trooper to the "I" frame, and discontinued the "E" frame version.
After this, the Trooper was available in either .38 Special or .357 Magnum with the frame mounted "I" frame firing pin. The .22LR model continued to use the "E" frame.
The Trooper continued to sell reasonably well up until 1969 when Colt discontinued all the old style "E&I" frame revolvers except for the Python."