RogerC, actually in a lot of pictures I can pick out the 5 screw guns by seeing the recess in front of the trigger guard. Counting the recess in front of the trigger guard, depending on the angle ofcourse.
4 screw descriptions to me have always classified the guns as having 4 screws in the sideplate, not 3 in the sideplate and one infront of the triggerguard. Until your picture I was unaware of any N-frames having only 3 screws in the sideplate as well as having the triggerguard screw to make a total of 4, almost all the N-frames that I've seen that had a triggerguard screw also had 4 in the sideplate as well making 5screws all have 4screw sideplates.
Trigger guard screws were dropped long before the 4th sideplate screw was dropped, from what was my understanding of S&W history.
So with the gun in the picture the trigger guard screw was something I had thought was long since history because the sideplate is a 3 screw sideplate.
To me it's a wierd gun, always thought the screw in front of the trigger guard screw left the guns long before the 4th screw in the sideplate. Maybe somebody can shed some light on this?
But the pinned barrel thing, lost me head there for a minute and forgot when the pinned barrel was dropped and thought that they were all dropped at the same time as when the 4th screw in the sideplate was dropped.