No. 73 grenade

The No. 73 grenade, also known as the "Thermos", "Woolworth bomb", or "hand percussion grenade", was a British anti-tank grenade used during the Second World War. It got its nickname from the resemblance to a Thermos flask. With the end of the Battle of France and the evacuation of the British Expeditionary Force from the port of Dunkirk between 26 May and 4 June 1940, a German invasion of Great Britain seemed likely. The British Army was not well-equipped to defend the country in such an event; in the weeks after the Dunkirk evacuation it could only field twenty-seven divisions. The Army was particularly short of anti-tank guns, 840 of which had been left behind in France leaving only 167 available in Britain; ammunition was so scarce for the remaining guns that regulations forbade any being used for training purposes. As a result of these shortcomings, new anti-tank weapons had to be developed to equip the British Army and the Home Guard with the means to repel German armoured vehicles. Many of these were anti-tank hand grenades, large numbers of which could be built in a very short space of time and for a low cost. They included the grenade, hand, anti-tank No. 74, also known as the "sticky bomb", which was coated with a strong adhesive and stuck to a vehicle, and the No. 76 special incendiary grenade, essentially a simple white phosphorus incendiary contained in a breakable glass container, like a more sophisticated variation of the Molotov cocktail (which simply uses a flammable liquid such as gasoline and a burning rag as a "fuse"). Ian Hogg states that the simplest of these grenades was the No. 73 grenade. The No. 73 grenade had a roughly cylindrical shape and plastic screw-on cap, similar to that of a Thermos flask, from which the "Thermos bomb" nickname was derived. It was approximately in diameter and in length, and weighed . Its explosive content consisted of of polar ammonal gelatine dynamite or nitrogelatine – both of which were highly flammable and could be detonated by the impact of small-arms fire.