WALLIS BARNES: (1887-1979) English scientist & inventor of the bouncing bomb used in Operation Chastise (The Dambusters Raid) on 16th May 1943. Signed Royal Air Force Museum cover issued to commemorate Barnes Wallis and featuring a colour image of an R-100 airship and with an inset portrait of Wallis, post marked 15^th June 1976 on the 40^th Anniversary of the first flight of the Wellington bomber. Signed by Wallis in bold blue fountain pen ink with his name alone to a clear area. About EX