This movement represents an early, short-lived experiment: the newly invented balance spring. Tompion omitted a fusee—a cone-shaped device used to even out the force in the timekeeping mechanism as the spring unwinds. His fine workmanship, the ingeniousness of his designs, and the greatly improved accuracy of his timepieces contributed vastly to the fame of English clockmaking in his lifetime. Nathaniel Delander was one of Tompion’s favored casemakers.