Excellent identification of this rare machine by Mr. Aerohydro. By the way I don't think your search techniques are faulty. There is literally very little available on Karl Hipssich and his invention(s) and what is available is in books which are copyrighted or in scanned old magazines which have not been indexed (no OCR). What complicates things further is of course sometimes the old German letters (Fraktur).
To give the history some flesh, this is what I could find.
Karl Hippsich (also given as Cäsare
Hippsich) was a German inventor who lived in Vienna. He had an interest in aviation and invented and patented a flying machine (Drachenflieger) which was automatically stable. Next to the USA patent I could find patents in Great Britain Patent 1909/17668 Flying machine
and Germany Patent 226932 Drachenflieger
. Surely there will be comparable patents in France and Austro-hungary, but given the time I could not locate them. This is an instance of documents which are scanned but not indexed, just as the German one. In this case I was 'lucky' to find a reference in an old magazine to the number of the german patent which can be accessed.
The patents show a flying machine that 'in which by the special shape and arrangement of the planes the stability of the machine is ensured under all circumstances
Hipssich designed a real life full scale realization of his patent (looking differently, with a tandem wing and no swept up wing tips for instance). This started end 1908 / begin 1909 where the actual billing was done by the Vienna firm of Karl Köhler. The completion was long - some one and a half year. The machine was first exhibited in Vienna at Makart atelier. This is the picture which is given for instance in Jane's 1913. It shows the machine complete with tandem wings and two pusher propellers. Engine was a 45 hp Dutheil and Chalmers. Proudly painted on the side of the machine is the name HIPSSICH.
There is another picture of the machine at the same place but not completely finished. It gives in great the detail the construction of the propeller part. Look at the handles in front. In front of the machine stands proudly the inventor Mr. Karl Hipssich, with a bowler hat.
The flight tests that started beginning 1910 at the Vienna flying field Wiener Neustadt were not successful, so extensive modifications were done using as much of the original as possible.
Changes included the reduction of the propellers to one only, a pusher propeller fitted between the tandem wings. The fitting of ailerons (Querruder) at the wingtips of the front wing, dual seating and other changes. The machine was changed out of all recognition to the original. The re-building was done by the Daimler Werke.
The Challenge picture shows the machine at the Vienna flying field Wiener Neustadt at the beginning of October 1910
. Again at right with the bowler hat is Mr. Karl Hipssich. At the left there is the pilot of the machine (Erich] Köhler who had no pilot license at that time. He acquired German No. 347 at January 10, 1913 at Breslau when flying a Rumpler Taube.
The easy way out to identify the machine is (as taken by Keimel) to differentiate with numbers (-I and -II). I would not do that and follow the contemporary 1910 text which identifies the machine as 'Der rekonstruierte Hipssichflieger
' [The reconstructed Flyer of Karl Hippsich - October 1910].