Bottom half of Redfield International Match receiver sight. Its back side has a 1/4” x 5/16” groove that would mount to a base attached to the rifle's receiver. There are two vertical holes (spaced 7/8”) in the front half of the base that contain fillers. I don't know if these are original or not. I'd guess not. No elevation plate or screws. Price: $8 shipped in the USA.