This coincidence of mark DUX and airplane industry is very strange. It is so strange I wonder if it is really some coincidence or something else... The connection is this sail-airplane called Grunau Baby (see Wikipedia) and the two places in Lower-Schlesien now in Poland: Jezow Sudecki (Grunau in German) and Gross-Glogau(w). So I wonder now to what airplane did DUX make parts? However, this Grunau Baby sailplane was introduced as late as in 1931 and you tell DUX continued with their industry in Germany only until early 1920s.
There are people who lived in St.Petersburg who had a part of their family history in Gross-Glogau and they might be relatives of those Grunau-people in Jezow Sudecki, both 'villages' in Lower-Schlesien - now the same voivodeship in Poland. This is the family that owned the DUX car in St. Petersburg and the family father was educated in the Technical Highschool of his time in St. Petersburg and wrote later books about all kind of motors when living in the West.
This family also had a young wife who, however, died in Vyborg 28.5.1928 because of an 'accident' that seems very strange for us people of today. Some air-plane poured all its fuel on her and she ended in hospital and died some days later. She was a daughter of a Scottish shipbuilding engineer by the name Stevens and I suppose they were British citizens. Also today some 'Stevens' has something to do with boats or yachts as has even some 'Grunau or Gruno', the same family-name in some different forms.
Sometimes it has hit me if this kind of a strange accident caused by some airplane didn't have anything to do with insurances... and how such a case might have ended... So insurances in times of about a 100 year ago might also be some kind of an issue.