the “M2 Alternative” printing, the red stripe on the cardboard packaging here is an instant visual identifier indicating the contents are M2 Ball cartridges; wooden crates of M2 Ball similarly bore the red stripe. Other colors used to identify non-ball .30 caliber cartridges during World War II included green-on-yellow stripes for tracer rounds, red-on-yellow for incendiaries and two blue stripes for rifle grenade blanks. U.S. color coding of ammunition packaging appears to have begun during or after World War I, but any specific beginning or end date of the practice is a bit obscure.