Sure ... Maschinen-Fabrik Augsberg-Nurnberg MG 18 TuF:
http://www.cruffler.com/Features/FEB-02/Maxim13mmTuF.jpgMaxim Flak:
http://www.kaisersbunker.com/cc/cc18c.jpg [sideview sketches]
http://media.photobucket.com/image/Maxim-Nordenfelt%2037mm/prion_photos/DSC_0034.jpgFinding good online images of the 37mm Maxim-Nordenfelt can be a little tricky because the name kept changing and/or has since been mis-applied to other autocannons (Hotchkiss or Krupp) in German service. If you want to search further, you might try:
* 3,7 cm Masch. K (3,7cm Maschinenkanone) -- Kaiserliche Marine name
* 3,7 cm M FLAK (3,7cm Maxim Flak) -- Deutsches Heer name
* 3,7 cm Flak M 14 (3,7cm Flak Modele 1914) -- Reichswehr name
BTW, there was also an experimental Gast-Flieger MG firing the same 13x92SR round as the MG 18 TuF. As the name (and air-cooled barrels) suggest, the twin-barrelled Gast-Flieger was intended for aircraft use from the outset. It's less clear whether TuF was actually meant to be aircraft mounted ... but, then again, this
is what-if