Yes and K and N frames are counted the same, but not I and J frames:
Screw numbering and screw count relative to frame size designations:
1st rule: The I and J frame screw numbers and screw counts are different from K and N frame.
Some of us I frame collectors count the main spring strain screw as the 6th screw because unlike the K and N frames which all have the strain screw, all I frames dropped that screw in the early 10950s. So it's a helpful identifier of an I frame gun's vintage. I'm not one that insists everyone must recognize or use the 6 screw term. But since GREEN FROG coined it, some of us that collect the 1950 evolutionary I frames use and appreciate the term.
Pre & Post war I frames were all 6 screws counting the strain screw, 4 screw sideplates and the 5th, the TG screw.
Baby Chief J frames were introduced as 5 screws with a coil main spring and no strain screw.
The I frame 6th screw was eliminated first with the Improved I frame c. 1952 (except the .22/32s which were not made on the improved I frame).
The trigger guard screw is the 5th screw because it was eliminated next on these frame sizes with the introduction of the Model of 1953 (.22/32s lost the 6th and 5th screws at the same time). So all I and J frames became 4 screw guns after 1953.
The 4th screw at the top of the side plate (called the "bug" screw at the factory) was eliminated next. So a 4 screw I and J frame has all four sideplate screws and can also be referred to as a 4 screw frame. After the 4th screw (upper sideplate screw or bug screw) was dropped they became 3 screw sideplate/frame c. 1956, while the K & N frames didn't begin to transition to 3 screws until the end of the 1950/early 1960s, when the TG screw was finally eliminated.
K & N Frames:
On 5 screw K or N frames the upper sideplate screw (bug screw) was the first to be removed, therefore it is the 5th screw. So, unlike the I and J frames, the "4th" screw is in the TG. Fourth because it was the second screw dropped c. 1960.
So a 4 screw K or N frame has only 3 sideplate screws and the 4th in front of the trigger guard; again, the top sideplate screw, 5th screw, being the one eliminated first.
2nd rule: Always count the screw under the right grip because it isn't covered by the grip on most pre war models and early post war models up to around 1950. It's a domed head screw when not covered by the original factory grips and a flat head screw when covered. In the early days of the Magna stocks, a relief dimple was drilled into the back side of the right stock panel to provide clearance for the round head screw before it was replaced with a flat head screw.
Exceptions:
1. Early K Airweight guns can be found with a "6th" screw, (adding confusion, it's also called "bug" screw by some gunsmiths) which is a lock screw for the top sideplate screw on similar to premium shotguns.
Since I frame Airweights weren't introduced until after their trigger guard screw, the 5th screw, was already eliminated with the Model of 1953 (except for a handful of Baby J Airweight prototypes), their "bug" screw on the upper sideplate (factory bug) screw can be referred to as a 5th screw and are the only Mod 1953 "5 screw guns".
2. The original K frames, .38 and .32-20 were 4 screw guns; all 4 sideplate screws but no trigger guard screw until the very late model of 1902, which introduced the 5th screw, in front of the trigger guard and are the scarce transition guns - about 10,000 of them. All became "5 screws" when that trigger guard screw was introduced on the 3rd Model M&P HEs (Models of 1905).
The 1902 has the old-style lockwork, which will have the rebound-levering-pivot stud showing about 1/2" below the cylinder release. In this picture, you'll see the stud end circled in red.
3. The new X frame 500 and 460s have gone back to 4 screws with addition of the top sideplate bug screw.
