Information on Multiple Makers

The Watch Guy - Provides history and/or serial numbers for various makers including Benrus, Bulova, Elgin, Gruen, Hamilton, Harwood, Rolex, Wittnauer, and some others.

Gruen Watch Sites

Gruen: The Art and History - This is easily one of the best sites I have found concerning the history of Gruen and their many watches. He covers from 1867 to 1958.