Troughton & Sims Folding Arm Protractor, Circa 1850 This exceptional folding arm protractor, crafted by the renowned British instrument makers Troughton & Sims of London, dates back to approximately 1850. Known for their precision and craftsmanship, Troughton & Sims produced some of the finest scientific instruments of the 19th century. This particular protractor features a unique rack adjustment mechanism for smooth and precise measurements, ensuring unparalleled accuracy. The instrument folds neatly for easy storage and portability, with a beautifully crafted original shaped mahogany case that provides excellent protection and showcases the piece’s antique charm. This item is a fantastic collector's piece, combining historical significance, craftsmanship, and practicality. Perfect for collectors of antique scientific instruments, this folding arm protractor is a rare and valuable addition to any collection.