That is the Model 1902 sight, which is the same as that on my 200722.

Is there a little peep sight that swivels up, on the back of the eyepiece? Most M1902 sights have it - those without are a bit more desirable.

Almost any Krag rear sight is "correct" on an 1898 rifle - they went through a lot of changes and overhauls. The test is that the finish color and wear should match the rest of the rifle.