Six inch Brass sector signed T Heath Fecit, decorated on hinge and legs with floral patterns

Six inch Brass sector 1720-1753 signed T Heath Fecit, decorated on hinge and legs with floral patterns. Sectors were used from the end of the 16th century until the mid 19th century to perform calculations involving proportion. They were inscribed with logathmic and trigonometric lines and lines used for drawing and calculating surfaces and volumes.