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.

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