The Mark-12 was notable for being significantly smaller in both size and weight compared to prior implosion-type nuclear weapons.
For example, the overall diameter was only 22 inches (56 cm), compared to the immediately prior Mark-7 which had a 30 inches (76 cm) diameter, and the volume of the implosion assembly was only 40% the size of the Mark-7's.
There was a planned W-12 warhead variant which would have been used with the RIM-8 Talos missile, but it was cancelled prior to introduction into service.
It is believed to have used a spherical implosion assembly, levitated pit, and 92-point detonation.
Though the weapon went out of service in 1962, it resurfaced in a fictional role in Tom Clancy's 1991 book The Sum of All Fears and the 2002 film, where the plot included an Israeli copy of the Mark-12 being lost by accident in 1973 during the Yom Kippur War in southern Syria near the Golan Heights, and then recovered by a terrorist organization.