In March, 80 years ago, production of the Bf 109 F-2 began. The F-2 was equipped with the MG 151 15 mm cannon before the harder hitting 20 mm version became available. A total of 1,332 were built with some receiving air intake sand filters in the field for tropical operations. http://pbs.twimg.com/media/ExBLifXWYAYzKiA.jpg