mostly-legible strike in blue on reverse of locally-addressed 1861 cover, franked with 1861 1c Blue tied by blue "Chicago Ills Aug 30" datestamp, additional blue Chicago backstamp as often seen on incoming mail, fine, only two examples of this handstamp are known on drop letters mailed three days apart (August 27 and 30, 1861), a rare cover and an early use of the 1861 issue from Chicago