Touchmark

For quality control, Parliament in 1503 required all London-made pewter to be stamped with the maker's symbol or touchmark.

The instrument used was a refracting telescope by Dollond. . . . The cap containing the diaphragm was furnished with a touch-mark consisting of a projecting spoke. When in adjustment as described above this mark was parallel to the short side of the parallelogram.

The initial touch-mark was established at Roper's saw-mill, on the North River, and is a point on 20-penny nail driven flush with the horizontal surface of sill to bull-wheel.