I checked through, "Die Flugzeuge de k.u.k. Luftfahrtruppe un Seeflieger 1914," and this is the list of planes which had the "Baby Coffin" for the Schwarzlose M.G.:
Knoller CII
H.B. C. I
Lloyd C.V
and of course, the Starstrutter. No Aviatik Berg D.I or Albatros of any sort had that armament, nor did the Phonix series.
Looks like a pretty thin list to me unless WNW is going for esoteric.
As far as I could tell there weren't any seaplanes with this arrangement either. The book was authored by Erwin Hauke, Walter Schroeder and
Bernhard Tötschinger.
My guess is the Hansa Brandenburg C. I, since CSM will be doing the H.B. D. I.
Not an expert, perhaps someone else on the list can find others?