I won this nice 1896 Krag in a live online auction just two months ago. The serial number range of 63xxx and cartouche show it was born in 1897. I had the auction house send me photos of the cartouches and they were faint but readable.
When I got it, I knew that the stock at some point in its long life was refinished since it looked a bit too nice for a former service firearm. Thus the cartouches can only be seen out in the daylight. Still, it has a nice bright and shiny bore and still retains a lot of original bluing on the barrel.
Here it is with a few accessories including a Krag bayonet--dated 1895 attached to an original Spaulding 60 rd cartridge belt, a period haversack with an original leather strap plus a reproduction canteen. The Spaulding belt was actually designed for mounted troops--hence the saber hang ring.
The description from the auction mentioned the following vague connection to a unit.
Unfortunately, besides the regular 4th US regular infantry regiment, the only volunteer 4th regiment I could find that participated in the Spanish American war was the 4th Illinois volunteer infantry. Since most volunteer units would have been carrying the older Trapdoor, the information in the listing was probably just B.S. provided by the original consignor, so I did not let it influence me. I haven't taken the time to research it any further yet.
Still, I won it for a $1000 bid with a buyer's premium of 18% for a total of $1180. This seems pretty much in line with what Kerz said about an 1898 and later Krag rifles running in the $1000 range with an M1896 bringing a slight premium over that. Before I even started looking for a Krag, I bought the following modestly priced collector's book on the Krag via Amazon. ($24.95)
The American Krag Rifle and Carbine (For Collectors Only®) 2nd Edition
You will see all kinds of prices, but a book like this will help one wade through the mass of misinformation posted by sellers.
Cheers