Inert 20mm German made, Dutch / United States export, armor-piercing discarding-sabot tracer round used in the M139 and HS820 derivatives. This 20x139mm shell casing is made of steel and is in good condition. Markings can be clearly seen. The M139 is the US designated version of the HS.820 which is a 20mm autocannon developed by Hispano-Suiza primarily for aircraft use, but more widely used in a series of ground-based anti-aircraft guns.
