I don't think there ever was an "Eissler Wien". The company name was 'Warchalowski, Eissler'. Osterreichischen Industriewerke Warchalowski, Eissler & Co. A.G. was founded at Wien-Ottakring in 1913 by August Warchalowski (President and Director General) with
ing. Georg Eissler. Their chief designer was the famous racer Otto Hieronimus - hence the name of Warchalowski, Eissler's best-known product - the Hiero (
not 'Hiro') brand of aero-engines.
During WWI, Warchalowski, Eissler & Co. A.G. expanded into munitions and ancillary military equipment (including field kitchens dubbed '
Gulaschkanonen').

I see no evidence to suggest that this expansion included the building of airframes.
So, what is flying boat pictured? Jos suggests this "Eissler Wien XXII" may be a Lohner-built
Typ K. It certainly has the outer V-struts of Lohner designs but those designs also had multiple strut bays - this flying boat didn't. Nor can I find evidence to suggest that Lohner ever built K-
Flugboote.
Most of the Austro-Hungarian W.13s were built by UFAG in Budapest. AFAIK, those UFAG-built boats all had parallel outer wing struts. A handful of
Typ Ks were built by Oeffag and Phoenix. I wonder, did those boats have outer V-struts?
Anyway, the
Typ K's powerplant was a 360 hp Austro-Daimler AD12 but production of that troubled engine was halted, leaving many motorless
Typ K airframes. So, here is a
highly-speculative possibility: At war's end, might the United States' war-booty aircraft have been an Oeffag- or Phoenix- built
Typ K experimentally fitted with a Hiero substitute engine? That would explain the Warchalowski, Eissler confusion and, perhaps, those pesky V-struts ...