Of all the anti-tank guns used during the Second World War, the 37mm Pak 36 was the most widely encountered. This one is displayed in the Land Warfare Exhibit at Duxford.
Developed in 1933 and issued to the German army in 1936, with 9,120 being available by the beginning of the war in September 1939 and a further 5,339 produced during the war.
I remember having a 1:76th version (20mm) because I had the Matchbox Krupp Kfz 69.