20" Vtg Art Deco Postal Telegraph Wall Clock Synchronous Hammond Clock Co Antiqu20" Vtg Art Deco Postal Telegraph Wall Clock Synchronous Hammond Clock Co Antique no glass no cord so we didnt test great patina!! vintage Art Deco Hammond Postal Telegraph Synchronous Electric Time wall clock. Manufactured by the Hammond Clock Company, these clocks date from around the 1930s. They operate using a synchronous electric motor. Some models featured a "bichronous" movement that included a spring to run the clock for up to 30 minutes in