1918 cover posted from 1st Cavalry Reg. to Geneva with very rare "bP.Oa/21.1.18", transit HQ FPO "bP.999/25.1.18", fr. with 25c Sower stamp and canc. with "TRESOR ET POSTES 504/9-2 18" at French PO of Salonica and arrival "GENEVE/8.IV 1918". Censored by French "OUVERT AUTORITE MILITAIRE/309" and rare Serbian type V "(39)" censormark.