POCKET OPEN-AIR MONOCULAR IN SILVER, French, c. 1825, with several poinçon hallmarks. Mounted with pendant ring, the device folds to a very compact 1-5/8″ x 1-1/4″ x 1/2″ (4 x 3 x 1.3 cm), and opens with hinged lenses on sliding support arm. It is a traditional “Galilean” optical design giving upright images of low magnification. In fine condition, it is an unusual form of miniature telescope. The French poinçon mark of the “tête de lièvre” (the head of a hare), which is applied twice here, firmly dates it to 1819 – 1838.