In the course of doing my clock appraisal work for valuemystuff.com in London and privately here in the USA I have come across a cottage longcase clock with a birdcage movement dating to circa 1740. The square dial signed, "John Warren, Ockhamto". The oak cased clock is legitimate and the dial is genuine. John Warren is not listed in the book of "Devon Clocks and Clockmakers" written by Clive Ponsford in 1985. The town name of Okehampton was abbreviated to Ochhamto for lack of space in the circle in which it was engraved. Brian Loomes lists two John Warrens who apprenticed in London, one in 1693, the other in 1706. One of these clockmakers may have found his way to that ancient market town in southern Devon, and just never was previously listed.
Since it is a private clock here in the US I cannot provide photos for you. I merely provide my personal observation for the Historical Society for informational purposes.