The only thing I know of to look at on a Krag is the single locking lug bolt.
It should be examined for cracks, by Magnaflux, dye penetrant, or the Poor Man's Magnaflux, a gasoline dip.
Unobvious cracks or setback can be found by looking to see if the safety lug - the guide rib - is in contact with the receiver. On an American Krag, it should not be. (Norwegian Krags were fitted with it in contact for the hotter 6.5x55.)