I would say this is the setup for a swivelling propeller on an airship. The British Parseval airships had them (but not with Salmson engines) as did the R23 class. It wouldn't suprise me if some French airships had the same thing given it's a Samson engine. The props could swivel to face down making the airship a helicopter of sorts. Whether or not the Germans, Italians or Americans did this I don't know.
Alan.