Military post offices on the Salonica front. PS fr. with 10c. french stamp, never cancelled, posted from "VOJNA POSTA*Br.111*19.12.16", via "VOJNA POSTA*Br.999*21.12.16" and "VOJNA POSTA*Br.999*22.12.16" with Serbian censorship "PREGLEDALA/VOJNA CENZURA (11)" to Geneve. Also 3-line red cross marking "CROIX ROUGE SEBRE/Bureau des Renseignements/GENEVE, Rue Pierre Fatio 25". The Serbian military offices were not supposed to cancel French stamps. Apparently the clerks at TetP 504 were instructed that they should only cancel the stamps on registered mail. Therefore no one was authorized to cancel the stamps on unregistered mail to Switzerland. Occasionally they were never cancelled.