M-12400

Augustus Prouty received a patent # 224,040 on February 8, 1880 for the latch and #235,963 on December 28, 1880 for the lock used with his knobs. The knob pictured is an inside knob as indicated by the "O"on the button. The button is unscrewed to remove the knob. The exterior knob had a different design, K-12500. See Antique Builders' Hardware page 179.