If the barrel is 22 inches and the front site is original, the Krag you have appears to be an authentic 1898 carbine! The serial number is definitely in the range of true carbines. It's not a guarantee but you can't have an authentic 1898 carbine if the serial number is out of the 120,000 area.

The 1898 carbine can have a variety of rear sites, so your "c" marked rear site can be appropriate also.

So, see what other experts say but things look good so far...

Good job at finding what might be a rare Krag!