Two of my 22's have standard hammer, and the other is a target hammer. As you know, they are the same revolver with the Trooper being chambered for 38spl and 22 (4" only), and the 357 a separate model (4" and 6"). I will have to dig through my catalogs to provide more information on the available options other than what you stated. The stocks are also different. I believe that I can cover the full range of years that they were available with Colt literature.
[This message has been edited by 22-rimfire (edited 04-06-2005).]
The major difference between the early versions of the 357 and Trooper is, the Trooper had the firing pin mounted on the hammer.
In fact, the .38 and .22LR Troopers were really nothing more than the Officer's Model Match with a different barrel and a less well finished action.
At some point, in order to simplify things, the Trooper .38 was changed to the frame mounted firing pin, like the 357 and Python.
I "THINK" (note the qualifier) that this change came when the 357 was discontinued in 1961.
The .22LR Trooper continued to use the hammer mounted firing pin up until it was discontinued in 1969.
The 357 was available with a blued finish, 4" or 6" barrel, and choice of target hammer and grips, or service hammer and grips.
It typically had a better polish and blue than the Trooper.
The Trooper was available in blue or bright nickel finish, 4" or 6" barrel, (the .22 was in 4" ONLY), choice of target or service hammers and grips.
All the Colt revolvers that were available with target hammer and grips used the same hammer and grip design.
The only difference was the Officer's Model Match and early Trooper models used a hammer with the firing pin mounted on it, but externally, they look just like the Python and 357 hammer.
All the early 1950's Colt target grips were the fully checkered First type.
The 357 and Python had walnut grips, the Trooper usually having very dark brown stained, hardwood grips.
Under the stain, these are a white-yellow fairly soft wood.