Auxiliary Air Force Lapel Badge No. 24508. WW2, United Kingdom.

The Auxiliary Air Force (AAF) is now known as the Royal Auxiliary Air Force (RAuxAF) and, together with the Air Force Reserve, is a component of His Majesty's Reserve Air Forces.
It provides a primary reinforcement capability for the regular service and consists of paid volunteers who give up some of their weekends, evenings and holidays to train at one of a number of squadrons around the United Kingdom. Its current mission is to provide trained personnel in support of the regular RAF.
Instituted on 9 October 1924, the first Auxiliary Air Force squadrons were formed in 1925.
The pilots of AAF squadrons were generally formed from the wealthier classes, as applicants were expected to already have, or be prepared to obtain, their pilot's licence at their own expense.
Pilots of the AAF were expected to join for a period of no less than five years and were required to fly a few hours every quarter and attend annual training for 15 days.
Each squadron was provided with a town base for training, and facilities at an aerodrome.
All serving members were required to wear the letter A on their uniforms.
The prefix "Royal" was conferred by King George VI in 1947.