Mount Vernon, Col., Aug 2, blue cds with matching grid handstamp tying 1874, 3Ā¢ green (s.e. at left) on cover to Columbus, O.; some light cover toning at left, otherwise Very Fine, while not a confirmed territorial usage, this is still the only surviving example of a postmark from Mount Vernon. EstimateĀ $150 - 200. $0 (Image)