not to open a can of worms, but there were earlier periods that complicates things.
In 1923, the Department of Commerce created a new top-level license, the Amateur Extra First Grade, that conveyed extra operating privileges. It required a more difficult written examination and a code test at twenty words per minute.
In 1933, the Federal Radio Commission (FRC)
reorganized amateur operator licenses into Classes A, B and C.
Class A conveyed all amateur operating privileges, including certain reserved radiotelephone bands. Amateur Extra First Grade licensees and Amateur First Class licensees with "unlimited radiotelephone" endorsements were grandfathered into this class.
Class B licensees did not have the right to operate on the reserved radiotelephone bands. Amateur First Class licensees were grandfathered into this class.
Class C licensees had the same privileges as Class B licensees, but took their examinations from other licensees rather than from Commission field offices. Because examination requirements were somewhat stiffened, Temporary Amateur licensees were not grandfathered into this class but had to be licensed anew
Then in 1951, the FCC moved to
restructure the existing three license classes (A, B, and C) into six new classes: Novice, Technician, General, Conditional, Advanced, and Amateur Extra. Each license class required two exams, one on theory and one on Morse code, and each license was valid for five years (except Novice). Until the advent of incentive licensing in the late 1960s, the Technician, Conditional and General classes shared the same written examination and the Conditional, General, Advanced and Amateur Extra classes shared the same operating privileges.
The Advanced class was earned after the General Class through passing the Element 4A theory exam.
Class A operators were assigned Advanced Class licenses following the 1951 structure decision.[9] Although existing Advanced Class licenses continued to be renewed, new licenses were not issued in the period 1951–1967.
In 1964, the FCC and the American Radio Relay League (ARRL) developed a program known as "
Incentive Licensing," which rearranged the HF spectrum privileges. The General/Conditional and Advanced portions of the HF bands were reduced, with the spectrum reassigned to those in the Advanced and Amateur Extra classes. It was hoped that these special portions of the radio spectrum would provide an incentive for hams to increase their knowledge and skills, creating a larger pool of experts to lead the Space Age.[citation needed] It did not take effect until 1968.
I remember back in 1976, when i became a Novice, there were some senior Advanced Class hams who were still somewhat bitter over the fact that they had once been Amateur
Extra First Grade licensees with some exclusive privileges back in the day, only to see Generals eventually be given full privileges in 1951, and then to have some of their phone frequency privileges
taken away and given only to the new-fangled
Extras in 1968... may not seem like a big deal to us today, but it clearly was to some of them ...
see:
https://en.wikipedia.org/wiki/Amateur_radio_licensing_in_the_United_States