W79 Artillery-Fired Atomic Projectile
The W79 Artillery-Fired Atomic Projectile (AFAP), also known as XM753 (Atomic RA) or the Teeny Tiny Tacnuke, was an American nuclear artillery shell, capable of being fired from any NATO 8 in (203 mm) howitzer e.g. the M115 and M110 howitzer.
Source: Wikipedia — W79 Artillery-Fired Atomic Projectile (CC BY-SA 4.0)