Small magnifier on tripod stand of 1875

A small magnifier on a tripod stand, executed in brass. The lens is working fine and can be set by a screwing mechanism.The case is engraved ‘J.H.W. 1875’, which refers to Jan Hendrik Wilterdink (1856 – 1931), a mathematician and physicist in Leiden. From 1878 and onwards he was associated as an astronomer and observatory in that city. Wilderdink is known for his observations during solar eclipses in various regions on earth.This lens probably served as a graduation present to Wilterdink in his earlier years.Case dimensions : Heigth: 4,5 cm, diameter 5,2 cm.