Gruen was proud of their nyc address as shown in 1929 catalog. Special diamond and platinum watches originated there. It also became the main U.S. address for Bulova. Was always and still is a diamond and jewelry trading center. I was prompted to verify 580 5th ave when I noticed a Gruen and a USA marked Bulova with similar Fifth Ave. marking. Apparently Gruen's platinum and diamond decorated cases came from a group making jewelry and cases here. I am guessing not owned by Gruen or Bulova, and Gruen used the location as nyc sales office.