The rank insignia for the U.S. Army in World War II were modified on January 8th, 1942 with the addition of the ranks of Technician 3rd Class (T/3), Technician 4th Class (T/4) and Technician 5th Class (T/5). On September 4th, 1942 a "T" was added to the standard chevron designs for these new grades. Although they wore chevrons similar to corporals and sergeants, technicians had no command authority or duties, and could not issue orders to regular sergeants, corporals or privates. The technician grades were deleted in 1948.
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I belive a T/5 ranking is equivilant to todays corporal. The Techs usually had some specialized training or eduaction...todays army now shows no distinction.