1950s, Lemania RAF issued monopusher S/S chronograph (armed forces of the United Kingdom). This watch, back engraved on its asymmetrical 40mm steel cases "6BB-944-3306" (6BB signifying that they were property of the RAF, and "944-3306" indicating "wristwatch"), was initially issued to navigators in the Royal Air Force and later to sailors and submariners in the Royal Navy. The Lemania 6BB-944-3306 was intended to fly, and thus has tritium hour dots and markers, easy to read in a darkened cockpit.Powered by the Lemania Caliber 2220, in which all functions of the chronograph mechanism start, stop and reset are engaged by a single pusher. Almost exclusively used in military chronographs, the Caliber 2220 was based on an earlier pocket watch movement, the Caliber CHT 15. The Caliber 2220 took the basic design of the CHT 15 and added extra shock protection. For a movement intended for military use, the Caliber 2220 is quite elegant to look at, with the same artful symmetry as the dial. Also, the construction of the Caliber 2220 echoes the outside: the balance with a Breguet overcoil is large, the levers and springs fashioned from sheet steel, all brushed for optimal functionality. Versatile and reliable, the Lemania 6BB had twenty years of service before being discontinued in the 1970s. Ours, with the case back designation "715/56," was the 715th issued in 1956. Strapped on military NATO style strap.