For a long time revolver makers built "trainer" versions of service revolvers so cheaper .22LR ammo could be used.
Colt made most service models with a .22LR counterpart.
After the war, they made the Trooper in .38 Special and .22LR, and the Trooper Mark III in .357 and .22LR.
Colt made trainer or service target models for the Police Positive, Police Positive Special, and Official Police in the pre-war days.
There were special non-Target revolver practice matches shot with .22LR service type revolvers.