Having the correct rear sight is one of the highlights of your new Krag. If nothing else was good, that alone is worth around $500. I have searched for them and know how hard an authentic 1896 Carbine sight costs. The shadow on the screw in the front of the rear sight makes it look like it doesn't fit. It should screw down flush.

Would you mind sharing what you paid for this?

I agree that it might be best to leave it as it is unless you find someone competent to glue the cracks. I have unglued a few that were done poorly.

Nice find, though!