GIBRALTAR: 1856 (24 Mar) entire to Porto (Portugal) 'per Sultan' blue Gibraltar double arc dispatch and '6' accountancy mark, , P &)O Sultan sailed to Southampton arriving on May 2 but the letter was not offloaded, and believing this to be an unpaid letter for Porto a boxed 'Returnfor/Postage' hs in red applied in London, arriving May 13. Taxed small '350' (reis)