'148Infantry' - I bumped an old thread titled "carbine side cover" that points out main difference, (thickness of tenon), between 1896 and 1898 side-plates. (This thread is visible immediately below your thread).

Note - A model 1898 side-plate will not fit on a model 1892 or model 1896 receiver, unless the tenon on the 1898 plate has been ground to fit into the earlier Receiver's thinner mortise.
(BTW - I do not recommend altering Krag parts and mixing parts across models).

Model 1892 and model 1896 side-plates have contour differences, that are readily visible on the inside.
Some 1892 early plates are numbered, and may lack a blind-hole for the ejector-pin.
I believe all 1892 plates are thinner at the top and lack the long 'feed ridge', found on 1896 and 1898 plates.

(Note - The model 1892 and 1896 side-plates will likely fit on a model 1898 or 1899 Receiver, but, the tenon fit would be sloppy. Cartridge feed might be altered).

Model 1892 Krags that were updated to 1896 features, possibly received model 1896 side-plates(?).

(Parashooter kindly informed me, I was using the word 'tendon' instead of the correct term "tenon". I appreciate the constructive observation and corrected the above post).