The Idflieg (Inspekteur der Flieger) designation system was used to classify German heavier-than-air military (as opposed to naval) aircraft from the early days of the Fliegertruppe/Luftstreitkräfte to the end of World War I. The system evolved during this period as new classes of aircraft came into use. The specific, official "name" of a Luftstreitkräfte aircraft type consisted of the name of the manufacturer, the designation allocated to its class or category, and finally a Roman numeral. Thus the first "D"-class aircraft built by Albatros was named the Albatros D.I, the second was the Albatros D.II and so on. Application A complication in identifying wartime German aircraft is that German manufacturers typically used their own designations; and sometimes gave experimental productions unofficial "Idflieg-style" class numbers, perhaps in the hope of production orders. The "Rs" (giant seaplane), and "CLs" (two-seater seaplane) designations of the Zeppelin-Lindau company are examples, as are the unofficial "Dr" designations of the experimental Euler triplanes, which remained prototypes and were never officially named. The German Navy had a system for classification of aircraft types but did not use this, nor the Luftstreitkräfte system, to specify particular aircraft types, preferring to use manufacturers' designations. Airships were outside either system, being individually numbered in the same way as German destroyers and submarines, mostly in the "L" series. As well as serving to identify types, Idflieg class letters were normally included as part of German aircraft serial number markings. List of Idflieg class letter prefixes A Originally applied to all monoplane aircraft. "A" type aircraft (for example the Rumpler Taube and Fokker M.5) were at no stage limited by any official specification apart from their wing layout; in practice most "A" class aircraft were unarmed two seat reconnaissance or training aircraft. Exceptions were the single-seat Fokker "A" types that became the "E" class fighters when they were armed with synchronised machine guns. After 1915, the "A" class gradually became extinct, as examples reached obsolescence and were discarded. Later monoplanes were included in the "D", "C" or "CL" classes, with equivalent biplanes. B Originally all biplanes. Not connected to any official specification, apart from the wing layout. In practice, later types in the "B" class were all low powered unarmed two-seaters, mostly used for training and other second line duties. C Two-seat armed biplanes (designation introduced by April 1915). This was the first new designation to be introduced after the outbreak of