Promo,
The '98 carbines were in a couple bolcks in roughly 33K to 37K S/N. The Kragheavies on the "other" list can give you better numbers. No cartouche is not a sign of an inauthentic rifle. It is the sign of a replacement stock, most likely done at one of the arsenals. There were a lot of modifications made, particularly to carbines. The US Army finally quit pretending that cavalry were going to fire their carbines in mounted charges, so they dropped the "saddle ring" around 1898 or '99. A lot of older carbines got called in for "upgrades" which included a new, no-cartouche stock, new sight, and for some of them, sling swivels.
Rifles and carbines both got rusty in Cuba - it rained every day and all they had to prevent rust was bacon grease. So they went back to arsenal for refurbishing.
The 1898 sight was calibrated for the new, hotter 30-40 round the Army adopted after the Spanish American War. It was a pretty strong load and rifles started blowing up. So most of the '98 sights got taken off and replaced with the 1901 sight.
And so on.
There is this guy 5 Mad farmers, who has primary source material on all the modifications done to the Krag. He says he is going to publish. Look for his book, it will be a monster.
jn