On auction , this late 18e century monocular spy telescope .It is made of brass and marked at the inner tube : Ramsden London and 1-2 which numbers are also on the eyepiece .They stands for 2 different magnifications, 1 = ca 8x and 2 = ca 16x enlargement .0 = lenscover . The view is excellent, clear and bright .Glasses are intact with no scratches. Telescope diameter : 4cm .Lenght folded down : 9.3 cm . Comes in a , what looks like , an original cardboard container . Please see all pictures as they are part of the description . Jesse Ramsden FRS FRSE (6 October 1735 – 5 November 1800) was a British mathematician, astronomical and scientific instrument maker. His reputation was built on the engraving and design of dividing engines which allowed high accuracy measurements of angles and lengths in instruments. He produced instruments for astronomy that were especially well known for maritime use where they were needed for the measurement of latitudes and for his surveying instruments which were widely used for cartography and land survey both across the British Empire and outside. An achromatic eyepiece that he invented for telescopes and microscopes continues to be known as the Ramsden eyepiece.