During World War II the British made extensive use of Thermos flasks to keep liquids warm for personnel who would go long periods without access to facilities to warm tea or soup. This included aircrew, AFV crew and glider crew who could all spend long periods locked down in their vehicles without a hot drink; a Thermos of hot tea was a godsend to these men and a way of fighting off cold and keeping alert.
The Thermos had been invented in 1892 by Sir James Dewer and consisted of two flasks, one inside the other, with a near vacuum between them that prevented the movement of heat. This meant that hot liquids stayed hot, and cool liquids cool. They became ever more popular in civilian life between the wars and by 1939 Thermos was the market leader in Britain. Once war was declared they moved their capacity over from civilian to military manufcture and amongst the designs used this black metal vacuum flask was the most common:
The Thermos has a wire handle to allow it to be carried (this is actually a post-war example and the handle differs slightly in having the angled bends near the top of each side, these being straight on wartime production):
The front of the Thermos has detailed instructions on how to use it, for both hot and cold liquids:
The lid unscrews and doubles as a cup (again the circular stamping inside the cup are indicative of post war manufacture), a large cork acts as a stopper for the Thermos:
The base of the flask is stamped with the /|\ mark, the manufacturer’s name and a date of 1951:
Although there are subtle differences between this and a wartime production example, they are small enough that I am quite happy to display this flask with my World War II display until I acquire an example of the older style.