WW1 (damaged) cover to Watford cancelled with the machine LONDON FEB 17 17 Received from HM Ship, No Charge to be Raised and showing the purple cachet CEN (5W) SOR used by 5 Wing Royal Naval Air Service. 

Enclosed single page letter addressed from No. 5 Wing RNAS

Nice having the letter to substantiate the squadron cachet - scarce item. 

Condition as shown: Badly torn, part cover missing

ID GB RN 21604