Years ago, there was an Ohio dealer, Howard Davis, who used to provide a lot of nicely used US setenant stamps from the 1970s and 1980s. I used to frequent his table at the local stamp shows. He didn’t have just one or two copies in stock. He had dozens or more copies for most of the setenant issues. I wondered where he got all of them. One day, I found out his secret.
He was a part time dealer at local shows. His main business was insurance. He had offices both in Ohio and Florida. He always bought commemorative stamps at the post office. He mailed a lot of documentation back and forth between his offices. He instructed the secretaries to use the commemoratives on the mail and save them. He controlled both the sending and receipt of the mail to make sure that he got these nice used setenant blocks of stamps that he used for his stamp business. Hence, the name “controlled mail.”
He was not the first, nor the last, person to do this. Some of the setenant stamps and other high denomination stamps that survive today are because two or more people coordinated efforts to use those stamps on mail and to make sure that the recipient did not throw them in the trash.
This even happens today. If you have two collectors who agree to trade stamps and they put nice commemorative stamps on the envelope to mail their stamps back and forth, that too is controlled mail.