The best way to determine if you have a FW frame is to measure the width (span) across the nose- front of the receiver knuckle where the cocking rod axles protrude- R was a designation- the FW frames will have the extra tapped and recessed holes at the front bar of each sideplate, the R frame will not. But be advised- there were two "rare?" frame exceptions known- see Houchins book- the experimental 7 pin hole lock plates (possibly a H&H tyre sear interceptor design prototype) and also the C frame a R frame but with the extra front locating/mounting machine screws as on the FW series- Smiths are, indeed, a puzzlement- the radius break (nice job of giving out dims. too) was about the transition move from Syracuse to Fulton- early Syracuse Smiths had the four corners of the barrel lump (or lug) at true 90%- a right angle in steel against steel traps stress at that point, milling a radius relieves the stresses and sends them "a packin') around the radius- see the angle of the breech face to watertable- a 90% but the intersection is also radiused, and for this reason- some cheap US hardware store doubles were not so machined, they are junkyard dawgs today--
