Unknown Manufacturer, Pittsburgh, Penna., Sep 9, Paid (1871) Hollow Shield. Beautiful example of this rare fancy blue machine cancel of unknown origin, tying 1870, 2¢ red brown on an unsealed advertising cover. "Paid" instead of year designation in postmark, bluish ink with almost complete offset on the reverse side of cover, Very Fine and choice, one of the classics of machine cancel collecting. Scott No. 146  Estimate $1,000 - 1,500. $0 (Image)