Surprisingly sharp for a mirror lens.
This lens was made in the USA by Perkin-Elmer, the same company that made the optical system for the Hubble Space Telescope. Because the lens is made of solid glass, it is extremely resistant to shock and vibration and weighs 1.5Kg or 3Ib 4.5oz. Sold for about $650 in the 1970's. The lens has M42-.75 rear flange, which accepts T mount adapters so that the lens can be fitted to any 35mm camera.
Bought used on eBay 12/10/2004