1856. unbound. 4 pages on oversize vellum, 19 x 13.5 inches -- a very scarce patent issued to William M. Henderson, April 8, 1856, a resident of Baltimore, Maryland, with two original highly detailed drawings, colorized on heavy wax paper identified as "IMPROVEMENTS TO SLIDE VALVE ENGINES" with a technological page devoted to the explanation on how Henderson's invention would function. Fine signature by the Secretary of the Interior, Robert McClellland, with all ribbons and seals intact. Near fine.
William Henderson was a mechanical engineer and inventor credited with designing and improving a slide valve engine, a force pump, hydraulic brakes, and components associated with the steam engine.