VMAIL
V-mail
V-mail, short for Victory Mail, is a hybrid mail process used during the Second World War in America as the primary and secure method to correspond with soldiers stationed abroad. To reduce the logistics of transferring an original letter across the military postal system, a V-mail letter would be censored, copied to film, and printed back to paper upon arrival at its destination. The V-mail process is based on the earlier British Airgraph process.The above text is a snippet from Wikipedia: V-mail
and as such is available under the Creative Commons Attribution/Share-Alike License.