'markthenav' - Welcome to the KCA forum! You have a very interesting model 1899 carbine.

Your Krag carbine, #226507 (if I am reading it correctly), was built around August to September, 1899, at the beginning of 1899 carbine production. It was in the initial run of 5,150 model 1899 carbines.

As first assembled, your carbine would have been fitted with the model 1898 carbine rear-sight. Very few model 1899 carbines retained this 'three sight-notch' rear-sight, because the 2,200 fps cartridge was abandoned, due to bolt-lugs cracking.

Most of these early model 1899 carbines were then fitted with a model 1896 carbine rear-sight and a rifle hand-guard.

Later, most were updated and fitted with a model 1901 or model 1902 carbine rear-sight.

You have a model 1902 carbine rear-sight, now. Only about 1,000 model 1902 carbine sights were made.

Your Italian walnut model 1899 carbine stock, with its 1900 'cartouche', possibly is not the original stock on your carbine. With all the rear-sight changes, it is likely your carbine was rebuilt or 'overhauled', a time or two.
It seems apparent to me, Springfield Armory saw fit to have Joseph Sumner Adams inspect and put a new 'cartouche' on your stock. The style of ('new') cartouche appears to be like those used from 1906 to 1915 on School and Constabulary rifles.

Now the best part - If your serial number is 226507, your model 1899 carbine is documented in the SRS data, collected by Franklin Mallory - (#226507 - model 1899 carbine - 02/19/1936 - Second Corps Area).