This replica is dedicated to Royal Navy Captain John Campbell, who developed the instrument in 1757.

Crucially his invention appeared at about the same time as the first accurate, portable chronometers - and the combination of the two transformed navigation from guesswork to science, saving countless lives at sea. This importance gave rise to the air of mystique which surrounds the instrument and its use, even in today's age of electronic wizardry.

Detailing is impressive, with hardwood handle and protective box, six shades of varying intensity, and a powerful telescope.

• Size: 20 x 16 cm
• Box: 26 cm