I looked up my directories - no "Riedel or Ridel" owned a mill in 1907 in the Saratov province. As the writer knows, I also looked up the other 2 surnames in St. Petersburg residents' director for 1913 and 1917, under various combinations of spellings and could not find either. Even palace servants are listed (in the alphabetical lists), since they are bona fide residents in the city palaces. Vera Beljakova-Miller