Overseas cap

A side cap is a foldable military cap with straight sides and a creased or hollow crown sloping to the back where it is parted. It is known as a garrison cap or flight cap (in the United States), a wedge cap (in Canada), or officially field service cap (in the United Kingdom and Commonwealth countries). It follows the style which originated with the so-called Austrian cap in the 1890s. There was also a previous version known as the "torin", which had a much more curved top line when viewed from the side. Both Austrian and torin types were distinguished by the inclusion of a fold-down section for warming the ears and back of the head in inclement weather. These two styles are still used by officers of some British units and continue to include this feature. In appearance the cap is similar to the glengarry, but differs by a lack of the tartan, or check trim, toorie, and ribbons typical of the Scottish cap. It has been associated with various military forces from the time of World War I to the present day, and various youth organizations. A convenient feature of this cap is that when the owner is indoors and no coat-hook is available, it can be easily stored by folding it over the belt or, unofficially, by tucking it under a shoulder strap.

Other terms for this cap in semi-official and or slang usage include garrison cover (USMC and USN), flight cap (USAF), side cap, overseas cap, envelope hat, piss-cutter (USMC and USN), chip hat, bider, cunt cap.

All ranks of the Royal Australian Air Force (RAAF) are entitled to wear the blue garrison cap with appropriate cap badge in service dress and flying dress uniforms. The piping of the garrison cap for air officers is light blue, the piping for all other ranks is solid blue.

The RAAF is the only branch of the Australian Defence Force entitled to wear the garrison cap.

In the Canadian Forces, the field service cap (French: calot de campagne) is defined by the Canadian Forces Dress Instructions as a "cloth folding or 'wedge cap'...Originally designed for wear during field operations and training, it may now also be worn as an undress cap with full and undress uniforms." The cap is worn as part of the undress uniform by students of Royal Military College of Canada, and as an optional item by all ranks of rifle regiments with ceremonial dress, mess dress, and service dress uniforms.

...
Wikipedia