Savage said:
a. Nobody used 3-inch reels on-air. None of the professional tape transports of the day - Ampex, Magnecord, Presto, Berlant-Concertone, etc. - would play really small reels without stretching the tape. Tiny reels produced too much tension on the tape. Most agency spots were played off "tension-type" large-diameter hub 5-inch reels. 3-inch reels were really a consumer-type item used for voice letters and home-type machines. If a 3-inch reel was encountered (and some advertisers used them to mail spots if they were really cheap) the tape was immediately transferred to a larger reel so it wouldn't be eaten on the first playback.
I would say that depends on what part of the country your were in, and market size, and timing. Yes, by 1967 we were basically in the CART business and there were not a lot of small reels in use.
I started in 1956. Rural south. We were up to our belly-buttons in 3-inch reels. I didn't know "spots" could live on anything else.
You got pressed microgroove discs of commercials if it was a national campaign, a national agency. If you were in Little Rock or Tulsa or maybe Indianapolis, even in the mid 60s you could still get some acetate ETs from local and regional agencies, though 7-inch and 5-inch tape reels were the delivery method of local agencies.
Yes, David was even more active than I was in the "Busman's Holiday" activities. In the era when we had 4,000 to 5,000 radio stations, I stuck my head in and sized up 300 of them. I've seen a few Taj Mahals and a lot of really crummy dumps!
When I went for a job interview, or if on my own time I just wanted to see a station, I developed my own routine for deciding if I was interested in working for a station.
I wanted to see two things in a station: The rest room.... and the engineer's shop and workbench. They were sure-fire signals about the integrity and skill of MANAGEMENT. If a station owner/manager was content with a dirty, smelly, stained up rest-room, you knew he/she would be a bitch to work for. If the engineers work space didn't exist, was not well kept, you knew you would not like the value system of the owner and/or the manager.