An exceptional find for the precision instrument collector, this early 20th-century rolling sphere planimeter was manufactured by the premier Keuffel & Esser Co. of New York and Hoboken, New Jersey. Bearing model number 4286 and serial number 918, this highly complex mechanical computing tool represents the pinnacle of pre-digital drafting technology used by engineers and surveyors to calculate the exact area of irregular two-dimensional shapes directly from maps and blueprints. The instrument is expertly constructed from solid brass and polished steel elements, complete with its intricate rolling frame, integration wheels, tracer arm, fine-adjustment bars, cylindrical counterweight, and its original locking key. All components fit precisely into their original, specialized wooden transit case featuring the authentic K&E paper label affixed to the inner lid. Physically, the mechanical components are in working condition, retaining a stunning, bright brass finish with minimal age-related patina, while the wooden presentation case shows moderate to heavy surface wear, including prominent scuffs, scratches, and an honest coloration earned through decades of technical field or office service. H 3.5", W 24.5", D 17.25". Please see photos for condition. From the Dale Beeks collection.