Dear Mr. Richter,
According to available records Tiffany & Co. did manufacture their own watches for a short period of time. Around 1874, with help from Patek Philippe, Tiffany Co. made their own watches, many with parts from PP, selling them under their own label and unmarked to custom watchmakers. Around 1879, the Tiffany watch making was merged with PP. There were approximately 20,000 watches made. Many are identified as a PP because of the parts used.