ShieldAzure a testudo of three shields Or in chief a Roman sword fessways of the like.
CrestThat for the regiments and separate battalions of the Army Reserve: On a wreath of the colors Or and Azure, the Lexington Minute Man Proper. The statue of the Minute Man, Captain John Parker (H.H. Kitson, sculptor), stands on the Common in Lexington, Massachusetts.
MottoUBIQUE IMPAVIDI (In All Things Undaunted).
ShieldThe field is blue, as Tanks belong to the Infantry. One of the earliest examples of the equivalent of a Tank was the old Roman Testudo made by joining shields together so that protection and mobility were obtained at the same time with offensive power. To indicate these characteristics of a Tank unit, three shields in gold are joined to represent the testudo, and to represent offensive power there is a Roman sword in gold.
CrestThe crest is that of the United States Army Reserve.
The coat of arms was originally approved for the 321st Tank Battalion on 7 May 1924. It was redesignated for the 309th Tank Regiment on 3 June 1931. The insignia was redesignated for the 420th Infantry Regiment on 16 November 1932. It was rescinded on 2 February 1959.