During World War II, women played an important role in the war effort by joining the Auxiliary Territorial Service (ATS) in Britain. The ATS was a branch of the British Army, established in 1938, which allowed women to serve in non-combat roles such as drivers, cooks, clerks, and telephonists. 

To distinguish themselves from other military personnel, members of the ATS wore a distinctive uniform that included a tunic with shoulder badges. These badges were made of brass and featured the letters "ATS" in bold capital letters. They were worn on both shoulders by other ranks, indicating their membership in the ATS.

The ATS shoulder badges were first introduced in 1941, when the uniform was updated to the Service Dress (S.D.) pattern. This tunic was made of a khaki wool blend and featured four pleated pockets, a waist belt, and a stand-up collar. The shoulder badges were placed on the epaulettes of the tunic and were a prominent feature of the uniform.

The use of shoulder badges in military uniforms dates back to the 18th century, when British soldiers began wearing cloth patches on their uniforms to identify their regiment. Over time, these patches evolved into metal badges that were worn on the shoulders, chest, or collar.

Today, the ATS shoulder badges serve as a reminder of the important role that women played in the war effort. They are highly collectible items for militaria enthusiasts and are sought after by historians and collectors alike. Whether displayed in a museum or worn as part of a reenactment uniform, these badges are a tangible link to a pivotal moment in history.