"Oldsoldier" - Some additional observations:

Your model 1899 carbine, serial #248910, was likely assembled around February to April, 1900.

(Poyer's tables have it in March, 1900.
William Mook compiled data that projected manufacture in February, 1900).

Your carbine was manufactured during an interesting period.

Its first rear-sight was likely the carbine version of the "3-notch" Dickson sight, (a.k.a. the model 1898 sight). This sight was built and regulated for the 'improved', higher-velocity, 2,200 foot per second Krag ammo.

This 'hotter' ammunition was blamed for causing cracked Bolt Locking-Lugs and was discontinued.
The "3-notch" sight was also discontinued and usually removed, because it was not correct for the trajectory of the regular 2,000 fps ammo.

Your carbine is also in the serial number range of U.S. Krags that were assembled with the "Head-less Cocking-Piece". This was an economy move that proved to be more costly than the manufacture of the regular Krag cocking-piece.

It is very likely your model 1899 carbine was arsenal 'refurbished' a time or two.
In the course of this work, it received up-to-date sights, hand-guard, and likely a reconditioned stock.

When Krag rifles and carbines went to the Armory, arsenals, or depots, for rebuilding/repair and upgrades, the guns were taken apart, parts re-finished, and new mixtures of correct parts were put together.

This can explain why your acceptance 'cartouche' is dated 1899, when your carbine was actually made in 1900.
(Since your Krag had already been in service, there was no need for a new acceptance cartouche).

Hey, we like pictures and learn from them. How about posting some photos of your carbine!

Attached photos: 1. View of a 'head-less cocking-piece'.

2. KCA carbine sight photo & guide.

---