Graduations- Circle graduated in Roman numerals I to IX (x 8) by 2 divisions and with the eight winds "T", "G", "+", "S", "O", "A", "P", "M". The alidade has a fiducial edge at each end. The circle is mounted on a green velvet covered wooden base 5.6" (14.3cm) dia. which has a conical brass tube 3.25" (8.2cm) long attached to the underside.
Sights-Two folding sight vanes 1.6" (4.1cm) long are mounted on alidade, each having a vertical slit.
Compas-Dia. 2.25" (5.7cm) mounted at centre of instrument. Fitted with a narrow blued steel needle 2" (5.1cm) long, with a brass pivot cap at centre. No graduations except for an arrow N-S inscribed on base of bowl.