No exact date yet but I think I've narrowed the time period. It would have to be after the development of a practical AC moter system so that would place it after about 1890 (AC motor invented in 1888)and it probably wouldn't be practical until the city had a good electrical power system. That was accomplished before 1920.
It may or may not be relevent, but the Austrian mint converted their presses from steam to electric power in 1907.