P.O Box 506. 1942 (Aug 18) Cover from Helsinki to P.O Box 506, Lisbon, the Thomas Cook forwarding address for mail from Occupied Europe to G.B, readdressed to England with a yellow forwarding label handstamped oval "THOS. COOK & SON LTD / 16 SEP. 1942 / BERKELEY STREET W.1". Franked Finland 3½m, a G.B 2½d ("TC/S" perfin) cancelled in London, censored in Finland and G.B. A scarce origin for mail to P.O Box 506.