I think this watch dates from the time when Gruen tried to expand to Europe, which has been the start of the Alpina collaboration. This was meant as a two way deal but it did not fly here in Europe. Mich too expensive to import the watches from the US, the same watch from either Germany or Switzerland was probably half the cost and quality was not worse. As far as I know all started in 1926 and in 1928/29 it was clear that this would not fly. These cases must be from that period.
Remember the photo of the Alpina meeting in Berlin with Fred 1929? -> http://www.gruenwristwatches.com/1929-g ... eeting.php
This was about the end of Gruen watches crossing the ocean eastbound...