Ellis Machine Cancel. Boston, Mass, Jul 12, 1912. Clear full postmark tying 2¢ Wash-Frank on window address cover with enclosure; piece missing from upper left of cover, otherwise Very Fine, postmark from a prototype machine developed by Warren E Ellis and briefly trialed at the Boston and Washington D.C. Post Offices, originally thought to be a experimental Doremus, known use of only a day or two in each city, rare. Estimate  $150 - 200. $0 (Image)