I believe it is a censor mark. Each censoring officer was allotted a number so that letters could be traced back to the person who allowed, or dis-allowed, a letter / card to go through the mail.
Another option was that a number may have been used at different hours of the day and a record of who was on duty at any given time could be traced back.
Second option is just a guess.
Chimo
Bujutsu
Posted 04/26/2014 3:04 pm
