Insignia Description
A Silver color metal and enamel device 1 1/8 inches (2.86 cm) in width overall consisting of a shield blazoned as follows: Azure (Teal Blue), a volcano abased Argent surmounted by a pellet charged with a mullet of the second; in chief a lightning flash fesswise Tenné fimbriated of the second. Attached below the shield a Silver curved scroll inscribed "NEMO VIGILANTIOR" (No One More Watchful) in Black letters.

Symbolism
Teal blue and white are the colors of Army Security Agency battalions and represent the former designation of the unit. The volcano symbolizes the area in the Pacific in which the unit served. The black sphere charged with a white mullet alludes to the coat of arms of Captain Cook who discovered New Caledonia, the island on which the unit was activated. The lightning flash refers to the mission of the unit and the orange color represents their former mission as a signal company.

History
The distinctive unit insignia was originally approved for the 306th Army Security Agency Battalion on 30 April 1959. The insignia was redesignated for the 306th Military Intelligence Battalion on 24 May 1990.

Source: The US Army Institute of Heraldry