What does the ace of spades represent on the infantry helmets?

Answer 1

A Spade, as in a deck of cards, represents the 506th Parachute Infantry Regiment, 101st Airborne Division.

Richard V. Horrell WW 2 Connections.com

A quick Google search on the subject reveals a site that tells about the use of the ace of spades in Vietnam. Apparently in fortune telling, the spades suit represents death or suffering, and thousands of ace of spades (spadeses?) were dropped over the jungles of Vietnam to assist in the psychological warfare aspect of the war.

The ace of spades is placed on the first person that the soldier kills. If a soldier has his ace of spades, he has not killed anybody yet.

It also stood for -DEATH-. During the Vietnam War, it was a common misconception among US soldiers that the Vietnamese believed the ACE OF SPADES stood for DEATH.

Which is WHY American troops would distribute ACE OF SPADES playing cards on dead VC bodies. While the Vietnamese did not originally associate the ACE OF SPADES with DEATH, the card did become an effective weapon in the psychological battle with the Viet Cong. As a symbol it was also a very effective tool in the maintenance of moral among US fighting men. In fact, leaving the card on the bodies of dead Vietnamese soldiers became such a popular practice among G.I.'s that the BICYCLE playing card company was asked to manufacture that single card and ship it to Vietnam by the crate. These crates where often marked with the label "BICYCLE SECRET WEAPON." The card could also often be spotted tucked into the helmet webbing of American Infantry and Marines.

Being apart of the 1/501st there is no significant meaning to any of the signs. It was a way the 101st ABN back in WWII was able to identify other regiments within the division. To this day we all still wear the identifiers on our ACH.