'Robidouxs' - Brophy's book, "The Krag Rifle", and Poyer's book, "The American Krag Rifle and Carbine", do a pretty good job of explaining the five (or more) variations of the model 1902 (Krag) rifle sight.

FWIW - My long answer to a short question:

Your reasoning is in the 'ball park'. There may actually be four 'leaf' variations, on the model 1902 sight. (There are also other model 1902 sight features that changed, which makes for a whole lot of legitimate model 1902 sight variations)!

The model 1902 sight 'story' is even more complex, in part, because two other sights would later be a source of repair parts.

The model 1898 sight, (which was discontinued, when the 'hotter' 2,200 fps cartridge that it was sighted for, was abandoned), is kind of the ancestor of the 1902 sight.

The original sight for the 1903, "Rod-Bayonet", Springfield was kind of an 'offspring' of the model 1902 sight.

These two mentioned sights were discontinued, but, they were to provide some parts that were utilized in building or in repairing model 1902 sights.

The model 1898 sight, designed by Lt. Tracy C. Dickson, had a leaf calibrated like most model 1902 sights. The numbers went to "20" with a line going through each number. However, the side of the leaf was smooth, (no serrations), and the eye-piece had three sighting notches.

The leaf and eye-piece from many model 1898 sights were eventually salvaged and reused. The leaf had serrations added to the left edge and the two outside sight notches were ground off.

These modified leaf and eye-piece assemblies were put on a model 1902 base and became a variant of the 1902 sight.
(The 1898 bases and springs likely became scrap and were bought up by surplus dealers, like Bannerman).
The original slide 'locking-knob' on the 1898 sight was un-slotted. These were likely changed to a slotted-type in the salvage process.

photos: A model 1898 sight and a model 1902 sight variant, that uses a modified 1898 eye-piece and Lt. T.C. Dickson

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