Nice model 1899 carbine King Carp!

Is there a 'scallop' machined in the stock around the bolt-handle or is that just a shadow in the photo?

Dick Hosmer is correct about the make-up of the rear-sight. You have a practical 'parts' sight for shooting.

Hopefully in time, you locate a complete model 1902 carbine sight (or just the 1902 carbine base) and a '3-notch' model 1898 carbine sight leaf.
This would allow you to restore a couple of rare Krag carbine sights.

A 1902 carbine sight would be credible on your carbine with its current hand-guard.

Great that you have the front-sight protector! You have nice wood markings and color match. I would not mess with wood finish.