Is the display of the frequency on a radio mandated by AMA or FCC?

I've always been under the impression that it's an FCC requirement to have a flag denoting an air or ground radio and the frequency number displayed, not an AMA. I have it on all my 72 MHz radios (it was drilled into me at a very young age to have the flag on the radio), and the flag is nice for a quick check of the wind when landing in your peripheral vision. My DX6 never came with a flag, but with a radio that selects its own frequency it would probably be a moot point.

I don't remember, but was a restricted radio telephone operators license (I think that's what it was called) required to operate RC back in the 70's and earlier? I know I had to have one when I first started flight training for my PPL in the mid 1970's but that requirement was eliminated soon afterward.

Hogflyer