Posters of original research, analyses, insights etc retain all rights to their work.
Such research etc cannot be used in any format without the written consent of the author.
Interesting indeed, particularly the fact that Oesterreicher manufactured for Otto Prutscher - or Prutscher designed for Oesterreicher - around 1930. Prutscher was one of the preeminent designers and artists of the Wiener Werkstätte.
And interesting that the specialist at the Dorotheum had no clue that Oesterreicher only produced until 1938 and the powder compact therefore can't be dated "mid 20th century".