As a further precaution, each branch of the Agency keeps a number of post office boxes rented under assumed names, and when the secret operative is ready to leave for his field of action, he is given the number of one of these secret Agency boxes, and told to address all reports to fictitious persons in care of this box.
The operative on arriving at his destination rents a post office box under his own name, and promptly sends the number to the Agency. The superintendent or assistant superintendent in charge of the operative sends instructions, salary and expense money to this box, using plain stationery and envelopes. AH letters