manuscript postmark with "Sh 16½" rate on folded letter from Cape Francis, Haiti to Boston, endorsed "p Cap Tesley via Portland", very fine, the earliest recorded Portland ship marking, letter from Walter Burling to Samuel Perkins, according to Harvard University the Perkins brothers "entered into a partnership with Walter Burling to form Perkins, Burling & Company; the firm traded in the products of slave labor including sugar, molasses, coffee, and cocoa, as well as enslaved people themselves"