The Seth Thomas Clock Company was very prosperous into the 20th century and was considered the "Tiffany’s" of Connecticut clock manufacture, even by their competitors. Between 1865 and 1879 they operated a subsidiary firm known as Seth Thomas' Sons & Company that manufactured a higher-grade 15-day mantel clock movement and during that period were major supporters of a New York sales outlet known as the American Clock Company. They also became a major manufacturer of tower and street clocks after 1872 and in between 1915 were manufacturers of jeweled watches.