Mitsuki HMC 400mm f/5.6 Canon FD- breech lock version. Japanese lens with 72mm filter thread. Has a built in metal lens hood . Could be adaptod for about £12 (eBay) to fit Micro 4/rds Olympus or panasonic cameras to give a super 800mm f/5.6 lens. This is identical to the Hoya, so can be considered as good optical quality.