This is one of the 20mm Cannon Shells fired by Mosquito II DD612, flown by my father (Group Captain R G Slade) on the night of 22-8-1942. My father and his navigator shot down a Dornier 217 E-4 U5 ...

50 caliber machine gun had been rendered obsolete by jet aircraft ... In 1956 the gun was standardized as the M61 20mm cannon and entered service with both the United States Army and Air Force.