Wait the Arado challenge ist not solved yet !!
I need to see an Arado L-I Trainer to compare it with L-II, unfortunately i couldnt fnd any in the web until now.
As announced this picture is the start of my post WWI collection. It depicts L IIa 58 D-1873 Took part in the Europa-Rundflug 1930, DVS Braunschweig (Pilot Stutz),crashed at Pau on the 23d of July. Its stamped on the back with Arado Handels GmbH, Werft Warnemünde, so im very glad having obtained it
Its also covered in the link someone here already gave:
http://histaviation.com/Arado_L_II.html