'Pathological set' of twelve objective lenses
circa 1920-1939
'Pathological set' of twelve objective lenses and brass control knob, each lens with a known defect, in fitted box, with separate telescope, all by Cooke, Troughton & Simms Ltd, for demonstrating the effects of imperfect lenses, probably c. 1920-1939. Also three home-made 'artificial stars' consisting of ball bearings mounted on rods on a wooden base. (One lens cracked.)