The number 3 referred to the size of the frame.
The No.1 was .22 R.F. six shot. The No. 1 1/2 was a five shot .32 R.F. and the No. 2 was a six shot .32 R.F., the No.3 was originally a .44 R.F. but had the centerfire offerings added later.
The No.3 was identified as The Russian Model, New Model Russian, 2nd Model Russian, Schofield (or Army Model) etc.
The Nos. 1 ~ 2 were tip up models.