This Thompson Center manufactured second variation rear sight assembly is for the Seneca muzzle loading rifle with the hole spacing 9/16" apart (center to center) and is in very good condition with light wear. The second variation rear sight has the second variation base and the first variation upper assembly. The mounting screws are sold separately.  (file photo)

Note: Thompson Center Seneca muzzle loading rifles with the following serial numbers have been observed with this part: 52191