cover 10c Brown (150), horizontal pair, natural s.e. at left, tied by two bold strikes of red negative geometric NYFM cancels (type G22) on 1873 blue folded letter to France, left stamp additionally tied by partly readable red 'Supplementary Mail' in octagon h.s., indistinct red N.Y. exchange office h.s., red 'London Paid' transit, red crayon '6' credit, Calais transit, various French backstamps, light soiling along horizontal cover file fold, otherwise fine, 10c no-treaty period cover to France doubled to 20c due to Supplementary Mail surcharge photo est.