There is at least one other receipt that has an imprinted RN-A8, Carter, Kirkland. It, too, is not on laid paper. One should note that the receipt and stamp seem to be of the same color, indicating an early order from American Phototype Company when they did both the stamp and the document. This ended in January, 1866 because of a protest of other stationers, who were losing business.
Also note that there is no dot of color in the right 2, evidence that American Phototype had multiple dies so they could print receipts like this in multiples of at least four.
