I don’t need permission to Prattle here, but I did back when speaking on the radio. The requirement at that time was an FCC 3rd Class Radiotelephone Operator’s License. This study guide was printed the year after I took the test. Looking through the study questions now, I can’t believe I knew any of this material.
https://www.worldradiohistory.com/Archive-FCC/FCC-Commercial-License-Study-Guide-1974.pdf
Many wannabe DJ’s had trouble with the test. I passed it the first time. The license is in a box somewhere. As I recall, the FCC dropped the test before I quit the business. All you had to do to get a license was fill out a form and send it in.