Isle Of Man. (Prisoner Of War Mail). 1915. Registered 'Prisoner of War' envelope addressed to Devon bearing SG 375, 3d violet tied by Peel date stamp '15th Jan 15' with 'R/Peel' registration label and oval 'Aliens Detention Camp/Knockaloe. I.O.M.' in blue on face. Herman Heiser was interned early in the war first in the short lived Stratford Camp and then Deepcut and Frimley Camps before being transferred to Knockaloe Camp. Scarce item of registered mail.