When they were attached to other army units, ATS girls wore the badge of that unit over the left breast pocket .The wreathed ATS badge was worn on the cap and a small ATS on each shoulder. The girl on the right is wearing the small Royal Artillery grenade badge which would indicate that she is part of a Mixed (Men & Women) Anti-Aircraft Battery. As above some ATS gunners wore the Royal Artillery white lanyard on the right shoulder, instead of the orange & brown ATS lanyard.
ATS girl gunners operated the "Predictors"; instruments which calculated the height, speed and direction of enemy aircraft,so the gunners could set their shell fuses. ATS girls were involved in many different military jobs from cooking and clerical work to lorry mechanics.
Women over 5ft 2in between the ages of 18 and 50 were eligible to join.
Princess Elizabeth, later to become Queen Elizabeth the second, was in the ATS..