The repeating circle consists of a circular polished brass frame, with two wooden handles. A detached U-shaped bracket holds a third handle. The index arm carries the index glass. The tangent screw, working against a spring-loaded stop, and the clamping screw are positioned on the back of the arm. The instrument has three index arms moving with a brass scale and a vernier on the inside of the limb; they carry the telescope and the horizon glass. One arm has a tangent screw working against a spring-loaded stop and a clamping screw on the back of the arm. Index-glass adjustment is made by a screw and on the horizon glass by capstan screws. The circle has three hinged index shades, in red, green, and orange, and three horizon shades, two red and one green.

Attached to the circle are two magnifiers on 76mm swivelling arms with two frosted glass shades. There is also a threaded telescope bracket with perpendicular adjustment by a rising-piece and a milled knob. The telescope is 160 mm in length with an inverted image and four cross wires, A second telescope is 91 mm long with an erect image. An extra drawtube is 46 mm long with an inverted image and four cross wires. The sight-tube is 84 mm in length with an adjusting pin and a green shaded eyepiece.

The instrument has a polished brass limb with an inlaid silver scale from 0° to 720° by 20 arcminutes. The repeating circle has two silver verniers measuring to 20 arcseconds, with the zeros at the centre. A polished brass scale on the inside of the limb measures to 180° by 5° on either side of zero.

The repeating circle is contained in a square fitted wooden box, with a trade label in the lid for Dollond and Co, 35 Ludgate Hill, 66 Old Broad Street and 5 Northumberland Avenue, London, and an oval handwritten label, ‘19B/b.07 Chapman Light Exchanged for Castoltedm’.

This instrument is similar to NAV0077. The U-shaped bracket was recommended by Mendoza Rios, and according to him first applied by Troughton.