The "J" frame is the Smith & Wesson small frame revolver such as the model 36 .38 special. The smallest frame, as in the model 36 Chief's Special.
1971
Smith & Wesson uses a letter system to denote the frame size of their current revolvers. A "K" framed revolver is the size of the Mdl 66 357 Magnum revolver. A "J" frame is smaller, used on guns such as the model 36 chief's Special. Letters earlier are smaller, later in the alphabet are larger.
A "J" frame handgun refers to the Smith & Wesson small frame revolvers such as the model 36 and to any other handguns of that size (Taurus, for example, has a virtually identical revolver) which are build on the J size frame. S&W makes K, L, N, and X frame revolvers In ascending order of size.
A K frame revolver.
Assuming it is .38 caliber and therefore a J-frame, and without knowing condition, $150-$300
I frame
The model 29 is one.
It is on the frame.
Medium
Frame, barrel and cylinder
It is not a J or K frame.
Yes, a model 66 is a K frame revolver.