Not a huge find in the scheme of things but interesting to me. Found in a field looking across the Thames estuary, a bit battered but still enough markings on it for me to try to do a bit of beginners research. Dated 1942, 20mm and manufactured by RH. I believe this to be used by the Spitfire and made by the Raleigh cycle Co, Carlton, Nottingham. When found I admit looking skywards and thinking what the pilot was aiming at when fired.