Lot
668 
Imperial Mail Marking Machine Co., "Boston, Mass., Jul 9, 1896", Type D-53 Involute flag with "C", bold complete strike on 2¢ green entire to Boston Mass., Very Fine and choice. Estimate $1,000 - 1,500.
THE FIRST OF USE OF AN INVOLUTE FLAG MACHINE CANCEL.
The involute flag with "96" year-date is pared with American's Type D dial with "1896", producing a double-dated error. It was in use only July 9 to July 14, 1896, when the Imperial dial was installed.
The Boston involutes were produced from just two flag dies: one with a spread field and another with an ovate field. The pairing of these two dies with four different dials produced for Imperial machines and Type B and D dials produced for American machines resulted in sixteen recognized varieties, in use from as little as a week to as much as two years.