This is an awesome original Italian Carcano Rear Sight Cavalry Moschetto Truppe Speciali for HEX Barrel.  There is a difference between the rear sight for the round shank and hex shank barrels.  These have been meticulously removed and properly identified for the hex shank barrels.  These will come with a set of original screws and the flat spring that is often missing. These are ready to bolt on. May require some fitting to your barrel.