Many sources claim origin as early as 1939. An early example of the phrase may date from 1937, before World War II. The US History Channel broadcast "" in 2007 included a shot of a chalked "KILROY WAS HERE" dated 13 May 1937. Fort Knox's vault was loaded in 1937 and inaccessible until the 1970s, when an audit was carried out and the footage was shot. However, historian Paul Urbahns was involved in the production of the program, and he says that the footage was a reconstruction.