Sector by Troughton, bras, engraved "Troug

Bras sector, early 17th century.

Bras sector, early 17th century.

Bras sector, early 17th century.

French sector, 1751-1774.

Bras sector by George Adams, 1756-1760.

Mathematical sector, 1700-1738.

Surveyor's sector, early 17th century.

Six inch silver sector, late 18th century.

Six inch silver sector, late 18th century.

Bras sector, 1600-1700.

Six inch bras and ivory sector, 1668-1742.