
| Type | Dummy |
|---|---|
| Projectile | steel, black, 1 copper driving band Projectile Markings: (stamped) H.W.B.CO. LOT-51338-2 3-1942 |
| Case | steel, knurled choke crimp, greenish brown lacquered, 2 holes |
| Primer | none |
| Headstamp | NECO 1943 20MM M21A1B1 |
| Notes | There is a wooden rod in the case which prevents projectile setback. |