Green envelope

Green envelope: The usual name in the war for the ordinary Army envelope, issued to men for writing home (from its colour). The letters in these were liable to censorship, first by an officer of the writer’s unit and then also at the Base, and were handed in unfastened. For letters on specially private affairs, which the writer might not wish his officer to see, another kind of green envelope was issued periodically, in regard to which the writer had to certify "on honour" that the letter contained no military information. Such letters were liable only to censorship at the Base. These green envelopes, being in demand among married men in particular, were often procured illegitimately by others and traded in, "Green Envelope Wallah" being the name for the sellers.