There were at least two Liberty ships named George Calvert
American Mariner, Maritime Commission hull number 20, launched in 1941 as SS George Calvert, but renamed almost immediately. Best known as a missile range ship in the 1960s, she served under various prefixes: TS, USAS, USAF, USNS.
SS George Calvert, Maritime Commission hull number 29, sunk off Cuba in 1942 by U-753.