Longman Dictionary of Contemporary English
box number
noun
EXAMPLES FROM CORPUS
▪ Each one was labelled with a box number and contained a large brown envelope.
▪ I never wrote to that box number.
▪ I wrote that night to the box number.
▪ So she wrote to the box number and suggested a date for a preliminary viewing to avoid disappointment or misunderstandings.
▪ You have to get letter heads printed, make it look good, have a fake box number.
Usage examples of "box number".
He wondered how many other people knew about the AMG papers and the vault and the box number in the vault.
Standing on the ore, he noted the box number on his clipboard and then brought it over to the courier.
We put an advertisement in the Brighton paper every week telling anyone who has been threatened with Protection to write to a Box number and they will get help.