Reproduction Springfield Trapdoor 1873 Model 1879 Rear Sight 1884 M1873 45-70
The hole spacing is a shave under 2 inches center to center (see pictures)
The windage adjustment is loose and needs to be either fixed with a punch or tapped for a set screw or some other method of securing it (see pictures).
See pictures for details and ask any questions you have. I'm here to help.