Found this while looking through a book by George H. Eckhardt entitled "Pennsylvania Clocks and Clockmakers", New York, Bonanza Books, 1955: "Thomas, Joseph - Whitpain or Norriton Twp., Montgomery Co. - Learned clockmaking with Griffith in Philadelphia and was established in his own business in 1830. Was early president of Montgomery National Bank. Some of the Joseph Thomas clocks are marked 'Penn Square'. Thomas, Isaac - Willis Town, Chester Co. - Born 1721, died 1802. One of the best and most prolific clockmakers of Chester County. Thomas, Mordecai - Willis Town, Chester Co. - Born 1767, died 1837. Son of Isaac Thomas. Followed his father's clockmaking for a while, but had many other interests." Hope this ties in with someone's line. Unfortunately not mine. Nancy