Template:Idflieg G, GL, K, L and N-class designations - English Wikipedia @ Freddythechick

G- class

AEG	G.I G.II G.III G.IV G.V
Albatros	G.I G.II G.III G.IV
Daimler	G.I G.II
Friedrichshafen	G.I G.II G.III G.IV G.V G.VI
Gotha	G.I G.II G.III G.IV G.V G.VI G.VII G.VIII G.IX G.X
Halberstadt	G.I
LFG	G.I
LVG	G.I G.II G.III
Rumpler	G.I G.II G.III
Schütte-Lanz	G.I
Siemens-Schuckert	G.I G.II G.III
Union	G.I

GL- class

Gotha	GL.VII GL.VIII

K- class

AEG	K.I
Fokker	K.I

L- class

Siemens-Schuckert	L.I

N- class

G = Grossflugzeuge (large airplane), GL = Grossflugzeuge Leicht (light large airplane)

K = Kampfflugzeug (battleplane), renamed as G-class, L = bomber midway between K/G and R-classes

N = Nacht (night)