A rare Prismatic, Singers's type, Pocket Compass, dating from c.1868. This type of compass was a development of Schmalcalder's Patent compass of 1812 which introduced the idea of using an optical prism, combined with a sighting vane, to improve accuracy when taking bearings. This compass has an oxidized brass case, green Singer's Patent style compass card, a jewelled pivot, an optical prism, and a folding sighting vane. It also has a manual brake and an automatic transit lock, which is operated when the sighting vane is folded down. The distinctive bright green card design was intended to enhance the night marching capabilities of the compass, and this type of compass was often used by the British Army from around 1860 to 1900. This particular example is quite unusual in that it is only 50mm in diameter. The vast majority of examples of this type of compass were larger, at around 70mm. It is also rare to see this type of compass with a Singer's card, as most were produced with a card of a much simpler design.
Singers's Patent Compass: Samuel Berry Singer (1796 - c.1875) was a master mariner from Southampton when he patented his unique design in July 1861. Its high contrast design was intended to be much easier to read in low light than conventional compasses of the time. He did not benefit greatly from his invention, the patent lapsed in 1868, and he ended his days living in poverty in Kincardine on the Firth of Forth.
In good condition and full working order, the compass finds north very well. With just some wear to the original oxidized finish of the case.