The frame size of a Smith and Wesson model 66 is K.
By the size and features
Yes
N
K frame
I believe it to be the K frame
Compare it to known examples.
K frame
The M19 is a medium size K-frame. The M28 is a large size N-frame, which was also used in producing the 41 and 44 magnums.
Size.
Yes, there are the same frame.
Would have to at least know the frame size.