A five inch diameter large format desk model Halden Calculex in good working condition in original, but scuffed, case, marked on lid ‘A. Halden & Co Ltd British Made’
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Fletcher Wallis sells objects and books relating to the history of science, medicine and technology from his unit at Admiral Vernon Arcade Portobello Road. He publishes books through Vernier Press, including Antique Medicine Chests, and Corkscrew Patents from 1795. He has been dealing for thirty five years.