1917 stampless cover to London, endorsed 'On Active Service', with an F. P. O. 10 B.C.A. 31 AU 17 squared circle datestamp made from the mutilated 'NENO' canceller. The cover has been endorsed “H. Duff, Lieut-Col, CPO” at the lower left. F .P. O. 10 was at New Langenburg at that time. This canceller, which replaced the mutilated RUO cancel, first being used there on 10 July 1917. A very rare cancel.