The GROL (General Radio Operator's License) is what used to be the First Class Radiotelephone Operator's License ("First Phone", as it was usually abbreviated). There were originally three classes: First, Second and Third, and there were also three classes of Radiotelegraph Operator's Licenses, also First, Second and Third.
Time was, up through the 70s or so, the FCC required every commercial radio and TV broadcasting station to have at least one "First Phone" licensee actually at the station any time the station was on the air. He was in charge of transmitter frequency, bandwidth, modulation percentage and such things. The folks who worked directly under him usually held Second Class Radiotelephone ("Second Phone") licenses, and the folks at the microphones usually held "Third Phones".
The First Phone tests were TOUGH. They were like the Amateur Extra tests in the 1960s, but with about three times the number of questions. The tests for the Radiotelegraph licenses were killers, too. They were aimed more at shipboard operating, and they had Morse code requirements: 25 groups per minute for the First Telegraph (random five-letter groups). Ships needed licensed Radiotelegraph operators aboard before they could cast off lines and get underway.
Both the phone and the telegraph licenses could be "endorsed" for Shipboard Radar and for Aviation Systems. With a First Phone and both of these endorsements, you could pretty much write your own ticket.
I had both a First Phone and First Telegraph in 1965, and the license certificates are still on my wall even though they've been expired for years because they aren't issued any more. Just the "GROL". I have one of them also, but somehow the "glitz" is gone.
Sorry for the long post, but I've been reminiscing!