Graduations-Semicircle graduated 0-180, 180-0 by 10'. 0-100, inscribed "Umbra Versa". 0-100, inscribed "Umbra Rekta". 4-12 inscribed "Poligon". The alidade 10.65" (27cm) long has a fiducial edge at each end. A suspension ring is attached to upper part of semicircle and there is a straight edge 12.2" (31cm) long at the lower part of instrument. A tripod mounting spigot is attached to underside of instrument.
Sights-Two sight vanes 1.95" (5 cm) long mounted on straight edge, one sight with a vertical slit with a rectangular aperture above (complete with thread), the other with a rectangular aperture (complete with thread) with a vertical slit above. Two sight vanes 1.95" (5cm) long mounted on alidade, one sight with a vertical slit with a rectangular aperture above (complete with thread), the other with a rectangular aperture (complete with thread) with a vertical slit above.
Compass- Dia. 2.35" (6cm) mounted at centre of instrument. Fitted with a narrow blued steel needle in form of arrow 1.75" (4.5cm) long, with a brass pivot cap at centre. Graduated to 8 points and quadrantally in degrees.