There is no such thing as a 3 digit 1896.
1892/1896. An 1892 altered to 1896 format. Those exist of course.
Can't just swap the rear sight if it's a model later than the 1896 - the handguard matches the sight base and the 1898/1901/1902 have a different size base. He'd have to swap handguard and sight.
Pictures? Serial? Depending on the serial I'm going to ask for some specific pictures.....
---------- Post added at 11:19 PM ---------- Previous post was at 11:17 PM ----------
That is completely correct. It's even worse than that - they played musical chairs with rear sights on guns before they were even issued. Wander through storage pulling and installing different ones. Large numbers of rifles were finished without sights and had them added later.
On the 1898 rifles, the later ones, the only one who knows what the "original" sight is would be Cleo. Assuming she still has her crystal ball.