Wartime incoming military mail / early Free French censored mail: 6 JLY 1941 "On Active Service" air mail cover on Palestine-made "DOAR" company manufactured airmail stationary from Indian Army FPO 90 (ASMARA, Eritrea) to Barclays Bank JERUSALEM, franked 9 Anna (back) per Indian air rate & tied by 3 strikes of FPO postmark + passed censor with officer's endorsement (triangular cachet on front); backstamped 9 JLY 41 BASE OFFICE 2 (KHARTOUM) transit; marked by Deputy Chief Field Censor (Egypt) on front.
Of note, probable routing via BEIRUT as per 2x numbered censor marks on back "C2383" in manuscript & "3-3886" handstamp, conforming to censor signatures M/s Type D (which start "23") and M/s Type C (which start "3", similar in font-style to period used handstamp in Beirut) and period use (earliest known censored mail in Beirut dated 13 July); here pre-dating Robertson's earliest known dates of use (Nov & Sept. 1941) for these notations + "C" ('censor'?) prefix undocumented - a discovery piece for censored mail; close proximity of last digit of the two censor numbers, "3" and "6" may conform to later-used habit of day-dating censored mail in Beirut by adding a "3" to the actual day of entry and day of exit from the censor.
Partly slit open at top. Rare origin, unusual Levant routing & curious association of 'Doar' stationary with unit in Eritrea. Significant postal history as Beirut liberated just on 12 July.