Ebony and brass octant.

Octant made by Spencer, Browning and Rust, London, about 1810. Ebony frame and limb with a brass index arm and fittings, a brass stop for the index arm; inlaid ivory plates on the crossbar and on the back of the frame. Signed on the ivory plate on the crossbar: Spencer, Browning & Rust London. Marked (stamped) at the centre of the scale (at 47°) SBR. Inlaid ivory scale from -2° to 99° every 20', measuring to 89°. Ivory vernier to 1', zero at the right. The tangent screw is on the top of the index arm; the clamping screw is on the back. Three socket shades (two red, one green). Index-glass adjustment by screw; adjustment of the horizon glass by lever, worm gear, and a milled clamping screw; adjustment of the back horizon glass by a lever, wing nut and a milled clamping screw. The sight vane has two pinholes and a swivelling shutter; the back sight vane has one pinhole. A capped screwdriver or pencil is missing from the crossbar. No box.