Before WWII, Colt assigned names to their frame sizes.
The factory often used names quite different than the public did.
As example the medium frame Official Police size was known inside the factory as the "41" frame, since an earlier ancestor was chambered in that caliber, but the public often called it the Official Police or Officer's frame.
The small frames like the Detective Special were usually known as the Police Positive Special size.
After WWII, Colt started assigning letter codes to the frames, and most people improperly carry those letter codes BACK to the pre-war guns, although that more or less works out OK.
Here's the Colt DA frame size and letter codes:
"Police Positive"
"Banker's Model".
These were made only pre-war, and were shorter framed and short cylindered guns chambered for low power rounds like the .32 and .38 S&W.
The early Police Positive and "D" type grip frame was shaped slightly different and later grips usually don't fit properly.
The "D" frame, Small frame:
The Police Positive Special
The Police Positive target models
Diamondback
Cobra
Agent
Viper
Detective Special.
The Commando Special, a rough parkerized finish Detective Special made in the mid-1980's, not to be confused with the WWII Commando.
Early models had full length grip frames. The Colt Agent and all "D" frames made after 1966 have the short, "stubby" grip frame, usually with grips that overlap on the bottom.
All grips within type interchange.
Here's the difference between the long and short grip:
The "SF" Small frame.
The SF-VI
DS-II
The Magnum Carry.
This was the replacement for the old Colt "D" frame.
This was a new transfer-bar action made of stainless steel.
Production was for only a few years until the model was discontinued in 2000.
Grips are "nominally" interchangeable with the "D" frame models, but there may be slight differences in fit along the back strap.
The "E & I" frame, Medium frame:
The Army Special
Official Police
Officer's Model target models
The 357
Trooper
Python
The rare first model Border Patrol
Marshal.
The "Commando" a WWII Official Police with a parkerized finish.
The E & I frame are virtually the same gun with only very small differences.
For that reason, most people simply lump these all together, since there is near 100% parts interchangeability.
All grips interchange.
The "J" frame, Medium Frame.
The Trooper Mark III
Lawman Mark III
Metropolitan Police Mark III
The very rare Officer's Model Match Mark III
Official Police Mark III
Second model Border Patrol, simply the Trooper Mark III with a different barrel stamp.
These were the new transfer-bar action guns introduced in 1969 to replace almost all the older medium frame guns.
These are totally different gun with NO parts or grip interchangeability with the older models.
Note that MOST people mistakenly refer to the Trooper Mark III as simply the Trooper. This is WRONG. The original Trooper and the Trooper Mark III are completely different guns and NO parts or grips will interchange.
The "V", Medium frame:
The Trooper Mark V
Lawman Mark V.
An upgraded Mark III action with a vent rib barrel, and a "short action".
Grips will NOT interchange with the Mark III guns.
The "AA" medium frame:
The King Cobra.
The "AA" frame is nothing more than the "V" frame with a different barrel, and was first made in stainless steel, later in blue.
The "New Service", Large frame:
The New Service
The U.S. Model 1917
Shooting Master.
The was Colt's pre-War large frame revolver.
Grips interchange in all versions.
The "MM" large frame.
The Colt Anaconda.
The Trooper Mark V, the King Cobra, and the Anaconda all use the same grip.
There were a good number of other Colt guns, but these are all based on the above models.
