A sheet film negative, possibly acetate. The submarine Sealion (1959) undergoing a refit in Admiralty floating dock AFD60 (1966) at Faslane. A close view of the E.M. log on the starboard side of the hull, taken from the floor of the dock. The log is partially extended and is covered by a canvas bag. An Admiralty copy negative of a whole plate photographic print. A vertical format negative.