Thomas Armstrong Prismatic Pocket Compass & Case c.1880
A rare Greencard Prismatic Pocket Compass, signed by Thomas Armstrong, of Deansgate, Manchester, dating from c.1880. It was made by F. Barker & Son and has their distinctive reversed 'S' post-1875 'Trade Mark London' logo at North on the compass card. Barker would have supplied the compass to Armstrong's, who would then have added their own details to the card. It is very unusual to see both the maker's and the retailer's signature on the card - Barker usually supplied their instruments unsigned.
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 with a push-fit lid, hand-drawn Singer's Patent design compass card, jewelled pivot, optical prism, and folding sighting vane. There are luminous markers at North and South, painted with a special compound (most probably ‘Balmain’s Luminous Paint’, patented in 1877), which was activated by exposure to very bright light, often created by burning a strip of magnesium ribbon. The compass comes with its original morocco leather case, lined with blue velvet.
The British Army used this type of compass from around 1860 to 1900. This particular example is unusual in that it is only 50mm in diameter. Most examples of this type of compass were larger, at around 70mm.
Thomas Armstrong & Brother, Manchester: Armstrong’s had been trading in Manchester since 1825, as jewellers and silversmiths. Around 1851 Thomas Armstrong expanded the business to include the manufacture of optical instruments. In 1868 he took his brother George into the business and changed its name to 'Thomas Armstrong & Brother'. This helps to date the compass to sometime after 1868, which also ties in with the Singer’s Patent style design of the card (Singer’s patent expired in 1868). During this period Armstrong's reputation was such that in 1891 the company won the contract to supply the War Office, the Admiralty, the Board of Trade, the India Office and the General Post Office (G.P.O) with scientific instruments.
In excellent, near mint condition and full working order, with just some minor wear to the original morocco leather case.