It's possible your young friend was faking it, or maybe he was sharing a job. We had that problem years back in the San Francisco area. You'd get half a dozen hippies doing that.
It wasn't lawful. Postal officials would fire them when they'd catch them.
No this was the Page Belcher Federal Building in Tulsa which was owned by the Post Office. The other Federal Agencies rented from the P.O.
This kid was very clean cut and I doubt the P.O. in Tulsa was too in to hiring hippies, at least in that era.