United States. (Netherlands - Transatlantic Mail). 1866. Folded letter written from Rotterdam addressed to New York cancelled by Rotterdam date stamp '9th July 1866' with framed 'FRANCO' and manuscript '135' Dutch cents on reverse and '10' in red crayon (credit to U.K.), routed via London with London/ Paid transit '11 Jy', endorsed 'per first steamer' with 'N. York. Am. Pkt./ 5' arrival 'July 21' with hand-struck '16 CENTS' in red on face.
Commencing 1st July 1866 it became possible to send letters from the Netherlands fully paid to destination in the U.S. through the British open mails though there was not a postal treaty between the U.S. and The Netherlands. The un usual situation lasted 18 months until a treaty between the two countries became effective.