No drilling, tapping or major alteration. Guaranteed to hold zero. Can be removed and reinstalled easily. Made in the USA of top grade military allan aircraft aluminum. Use Weaver type rings (not included).  Won't fit Lang Vizier Rear Sight - Use 1890 mount for Spanish 1893.

Installation instructions for the 1916 Spanish Mauser

Push the side pin out of the rear flip up sight. Remove the spring by sliding it forward and lifting it out. Slide the flange nut into the undernut at the rear of the sight where the spring was. Place the mount over the flange nut. Line the side hole in the mount up with the holes in the side of the receiver and push in the pin you removed from the flip up sight.

 Place a pin, drill, etc. through the countersunk hole in the top of the mount and into the hole in the special nut and move the nut around with the pin until the round part of the nut slips into the counterbore in the bottom of the mount. Put the 10-32 x ½ flat head screw through the mount and into the nut and tighten this screw. Put the 10-32 x ½ set screw down through the front tapped hole in the top of the mount and tighten against the receiver. This screw puts pressure against the pin thus removing any play in the mount.