Brass and Steel Dial-indexing Engine

Dial-indexing engine, with pivoting brass and steel arms and an adjustable thumbscrew-tightened pin, and rings of holes for the accurate and regular division of watch dials.

T. R. Crom discusses this tool in detail in Horological Shop Tools 1700–1900, Vol. 2, pp. 424-425, fig. 857, where it is explained which purpose each division ring serves. The division rings, in powers of ten, indicate a date and origin in France between 1792–1795 during the French Revolution, when French law required ten-hour dials (and 100-minute hours) due to their re-design of timekeepers and calendars. The timekeeping system proved very unpopular, was only mandated during these years, and abandoned thereafter.