The design of the Army's Utility Shirt was revised in 1963.1 Clip cornered pocket flaps replaced the original straight flaps and the button spacing was improved to reduce undershirt visibility. Made from 8.8oz, rather than 8.5oz, cotton sateen, the new shirt also boasted back darts and adjustable sleeve tabs.2
1. Military Specification MIL-S-3001E. (12 April 1963)
2. Some P63 Utility Shirts were produced without the adjustable sleeve tabs.