The rifles used by the troops are M-16s, which was not deployed by the U.S. military until 1963.
At the beginning of the funeral procession, a man is shown purporting to be a French soldier. He is wearing a French red beret with the insignia of "Mad" Mike Hoare's 5 Commando, a mercenary unit operating out of South Africa during the 1960's.
During the funeral procession, US Marines are shown wearing enlisted insignia containing crossed rifles. The crossed rifles device was not added to enlisted insignia until 1959.
When Walter is courting Verna, his holster is empty. It is highly unlikely an Army officer would wear an empty holster during time of war. The officer would have kept his pistol (a Colt .45 ACP) in the holster.