Replica of the hand-operated, speculum grinding/polishing machine designed and constructed by William Herschel, circa 1780, to produce high-quality parabolic mirrors for the many 7-foot reflector telescopes constructed in his workshop at New King Street, Bath. These small, parabolic mirrors, with an aperture of around 150mm (6-inches), were shaped and polished by Herschel from the castings that he made in speculum alloy. A 7-foot Newtonian-type reflector telescope, using a 6.2 inch diameter paraboloidal mirror, was used in Herschel's detailed stellar survey and led to his discovery of the planet Uranus in 1781.