1852 (Dec. 12) Augusta, Ga. to Belfast, Ireland, folded letter with blue "Augusta Ga. Dec. 13" cds with matching "Paid" and "24" rating h.s., New York red "3" credit h.s. to G.B., carried by Collins Line Arctic from New York Dec. 20 to Liverpool arriving Jan. 1, Liverpool (1.1) backstamp and "ABOVE ½ Oz." straightline h.s., manuscript "1" due rating for additional rate only, London (1.2) and Belfast (1.2) backstamps, Very Fine. Estimate  $500 - 750. From February 1849 until December 1852, an informal agreement existed between the Liverpool and New York post offices regarding insufficiently prepaid mail. This agreement was not sanctioned by either government. Contrary to the wording of the postal convention which prohibited partial prepayment, these two exchange offices allowed letters prepaid at least one full rate to receive credit for the prepayment and be forwarded to the other office. Here they were marked for the unpaid additional postage. This resulted in some examples of both credit and debit markings on the same letter, and in a collection of less than the full amount.When the two governments discovered this private arrangement, the tried unsuccessfully to agree to a modification to the convention to legally permit this practice. By the end of 1852, each ordered its exchange office to cease the practice.One of only six recorded covers showing this part-paid treatment. New York considered the letter required only one rate and sent it to Liverpool with a 3¢ credit for the single rate prepaid. Liverpool marked the letter "ABOVE ½ OZ." and allowed the single prepaid rate. One shilling for the second rate was the only postage due. $0 (Image)