Became a watch collector 1979 after scrap value purchase of an 1872 Grossmann in a fine gold presentation case. Was told by a friend it was rare and valuable. Read about Moritz Grossmann and his watch designs that were used by cooperating German makers Assmann and Lange. For more than 30 years these 2 made essentially the same watch. Dietrich Gruen quit his Columbus Watch Co. 1895 to make his own Gruen watches and used Grossmann mechanical designs and production at his production facility in Dresden staffed by Assmann. So he had a fine quality product initially until 1902 when they started using the Swiss based Aeby & Landry and then their own Swiss factory. The expensive German made movements were great for quality reputation but slow sellers. Serial range 62000-67000 in 18, 16, 10 sizes. Mostly 18s, rare in 10s that son Fred Gruen did well with the Swiss Verithin models and w.w.
I consider the first Gruen p.w. to be the same quality of those from the 3 Germans made at the same time. But they are collector valued much cheaper. Why? Samples 18s, 10s 16s, Grossmann, Assmann, Lange much newer ad copy. artb