That ad is of a typical 1940s garage door opener, there were lots of them, but you don't see them prior to 1940. I've quoted before from the HEINL RADIO BUSINESS LETTER October 1938 where FCC Chief Engineer announced an informal meeting about a month before Part 15 was created:
"Mr. E. K. Jett, Chief Engineer of the FCC, acted as Chairman of the meetings and stated that for a number of years the Commission has been confronted with requests for rulings as to the legality of operating certain radio frequency devices without radio station licenses."
I suggested those "certain radio frequency devices" he referred to as to have been already been operating in questionable legality for years, had to be the wireless AM phono-occillators, because they had been around for years and there appeared to be no other products to fit during the 1930s - so it had to be them.
But.... Apparently, to my surprise, there were two radio-controlled garage door openers as early as 1930. Popular Science Feb 1931 Pg 32, tells of two inventors, independent of each other came up with it at the product at the same time
That really surprised me, but had they ever been marketed prior to the 1940s? (I had never come across any ads for them prior to 1940). Well, an even earlier article in Automotive Replacements magazine, February 1930, Barber-Colman announces they will be marketing their first product, which was a radio control garage door..
So yes, there were wireless radio garage doors openers in the early 1930s.. but were they a popular item? In one history of the Barber-Colman Company it indicates they never took off:
. " The first product was a radio operated electric garage door opener controlled from the dashboard of a car. Unfortunately, it was too expensive to be practical at the time. ..."
https://www.eprinc.net/history-barber-colman-company/
But this other museum issued Barber-Colman history said they were actually hot sellers:
NUGGETS OF HISTORY
Volume 49 March 2011 Number 1 (page4)
https://www.rhsil.org/uploads/2/6/4/3/26435469/2011_-_vol_49_-_no_1.pdf
"... Colman, newly intrigued by the potential of radio signaling and codes, developed a garage door opener that operated when a radio signal was sent from the car to the opener. The door was a strong seller and the small synchronous motor within it soon found its way into
other projects. ..."
The evidence indicates the former is correct, there's simply no indication of electric garage door popularity during the 1930s, not a single advertisement to be found (although did find metions) and no metion in popular culture of the time either.
So no, the "legality of operating certain radio frequency devices" commented about by FCC Jett in 1938 that led to the creation of Part 15 a month later was indeed the wireless AM phono-occillators - not the then extremely rare wireless garage door openers of the time. Nevertheless, still an interesting discovery.
The RF Cafe highlights an interesting 1933 Radio Craft article, https://www.rfcafe.com/references/radio-craft/new-radio-garage-door-opener-september-1933-radio-craft.htm It looks like the doors slid open as opposed to raised into the ceiling.
This made me wonder +again) if there had been any other possibilities I hadn't considered, like the RF plane flying hobby.. A quick look around shows it began as a sport in 1937 but it always required a licence untill the late 1940s when the FCC gave them Part 15 27.255 MHz. Same went for model boats
The TV and radio remote controls had also all been wired with extension cables until 1939. So, yeah.. The wireless low power frequency devices which Chief Jett had said had been operating for years illegally had to be the popular wireless phono-occillators which began being marketed no later than 1935.
But no, the part 15 rules weren't actually created specifically for the hobby AM transmitter, but it had already been a standing issue which Philco appears to have pushed to the forefront when they hesitated to put their new wireless radio remote control on the market because of the legal issues. General Electric apparently just ignored the legal ramifications when they put the first manufactured wireless phono-occillators on the market it 1935 - and somehow got away with it, even though they were illegal until November of 1938.
Anyway the first Part 15 device ever.. was the low power AM transmitter.