first USAF dress uniform, in 1947, was dubbed and patented "Uxbridge blue" after "Uxbridge 1683 blue", developed at the former Bachman-Uxbridge Worsted Company. The current service dress uniform, which was adopted in 1994, consists of a three-button coat with decorative pockets, matching trousers, and either a service cap or flight cap, all in Shade 1620, "Air Force blue" (a darker purplish-blue). This is worn with a light blue shirt (shade 1550) and shade 1620 herringbone patterned necktie. Silver "U.S." pins are worn on the collar of the coat, with a surrounding silver ring for enlisted airmen. Enlisted airmen wear sleeve rank on both the jacket and shirt, while officers wear metal rank insignia pinned onto the epaulet loops on the coat, and Air Force blue slide-on epaulet loops on the shirt. USAF personnel assigned to base honor guard duties wear, for certain occasions, a modified version of the standard service dress uniform that includes silver trim on the sleeves and trousers, with the addition of a ceremonial belt (if necessary), service cap with silver trim and Hap Arnold Device (instead of the seal of the United States worn on the regular cap), and a silver aiguillette placed on the left shoulder seam and all devices and accoutrements. The Airman Combat Uniform (ACU) in the Operational Camouflage Pattern (OCP) replaced the previous Airman Battle Uniform (ABU) on 1 October 2018. Awards and badges In addition to basic uniform clothing, various badges are used by the USAF to indicate a billet assignment or qualification-level for a given assignment. Badges can also be used as merit-based or service-based awards. Over time, various badges have been discontinued and are no longer distributed. Training All enlisted Airmen attend Basic Military Training (BMT) at Lackland Air Force Base in San Antonio, Texas for weeks. Individuals who have prior service of over 24 months of active duty in the other service branches who seek to enlist in the Air Force must go through a 10-day Air Force familiarization course rather than enlisted BMT, however prior service opportunities are severely limited. Officers may be commissioned upon graduation from the United States Air Force Academy, upon graduation from another college or university through the Air Force Reserve Officer Training Corps (AFROTC) program, or through the Air Force Officer Training School (OTS). OTS, located at Maxwell Air Force Base in Montgomery, Alabama since 1993, in turn encompasses two separate commissioning