Did Simon Willard put a mark on his Banjo clocks and where was this what did it look like?

Yes, Simon Willard did put a mark on his Banjo clocks. The mark was typically located on the inside of the door or on the back of the movement. It usually consisted of the words "Simon Willard, Boston/Roxbury" in block letters, along with the date of manufacture. In some cases, the mark also included a serial number. The mark was typically stamped into the wood or engraved into the brass.