By A Mystery Man Writer
This particular 20mm casing was manufactured in Raleigh Cycle Co., Ltd., Nottingham, England, UK The “OeZ” marking means “Oerlikon, Loaded with Nitrocellulose powder”. This marking was used to differentiate the semi-rimmed Oerlikon rounds from the similar looking (but not interchangeable) 20m Hispano. In British service, a “Z” stamped on the base of a case 20mm or below in caliber indicates that the case is loaded with nitrocellulose flake powder. This is opposed to the typical British Cordite “spaghetti” rod-type propellant.
What was the point of changing the Sherman's gun from a 75mm to a 76mm? - Quora
WW2 1944 British Dated 20mm Oerikon Ammunition Shell Casing
Heavy Ordnance Catalog
20mm Cannon Shell – Tales from the Supply Depot
Search 307 Ammunition for Sale in Manchester- Gunstar
Search 267 Ammunition for Sale in Greater Manchester- Gunstar
USA 20 mm/70 (0.79) Oerlikon Marks 1, 2, 3 and 4 - NavWeaps
20mm hi-res stock photography and images - Alamy
WW2 Canadian Dated 20mm Ammunition Shell Casing