This a multiball loading of the .321 Greener. It was developed by W.W. Greener and was made from a modified .450-31/4â€ Nitro case. It dates from the mid-to-late 1920â€™s and was not a commercial success.
The distinctive longitudinal flutes retain the 3 projectiles. Note the top 2 bullets have a coned hollow base to accept the nose of the next projectile. The rearmost projectile is retained by a stab crimp at the bottom of each flute.
Note the use of cordite powder, and a Berdan primer.
This round was not headstamped.
A single ball loading was also made. This was a 155 gr. softpoint loading.
Reference: Hoyem, George, 1991, The History and Development of small arms Ammunition. Volume 3. Page 135.