'King Carp' - I'm sorry to disagree with 'Whig' and report negatively on your rear-sight, but, I am sure it is a FAKE.

IMHO - The "C" on the base is the wrong font. The "20" on the leaf is also a different font than the other numbers and the spacing of the index line with the 20 looks wrong.

The #4 on the side of the base appears tilted and hand-stamped.

I believe your sight-leaf has the 'high hump' at the pivot screw. This is an early model 1896 sight feature. Too bad if someone doctored one of these hard to find sights.

Whoever made this is an 'advanced faker'. He altered the sight slide so it has the 'step-down' area bracketing the "V" notch, like a carbine slide.

It would be fun to examine this sight directly, next to a real McCoy!