Registered airmail cover with manuscript 'Correo de Internados' at top and 'Rem Otto Carben, Campamento Militar, Sierra de la Ventana. Est: Sierra de la Ventana, Provincia de Buenos Aires, Argentina' return address on reverse, (Otto Carben was an engineer in the 7th Division aboard the Graf Spee captured after the sinking of the ship and held in the Sierra de la Ventana concentration camp), franked with 1940 1.25p green, 1942 40c purple & mauve & 1944 5c black (SG 692, 712 & 743) tied by SIERRA DE LA VENTANA B.A. cds's dated 8 JAN 1945 with printed 'MINISTERIO DEL INTERIOR' registration label alongside. Addressed to 'Familie Arthur Carben, Roskow, GERMANY', censored in the USA with clear tape censor strip and in Germany with small red censor mark on reverse. Very scarce.