[Tubejunke]

Sounds like you are reading the manual right. I got out my Sylvania Technical (tube) Manual from 1958 to look up the pin configuration for the tubes. I could only find reference to the 21FDP4 and it only uses pins 1,3,4,6,7 & 8. No #2 there to worry about causing destruction by mis-jumpering .

There may be a physical pin #2 on your tube, but it has nothing connected internally. No worries there. Pin 6 on this tube is the G2. I don't know how similar the two tubes are, but this information at least confirms your interpretation of the book is correct. I wonder if the AP4 is electrostatic focus and

By reading my book it looks as if what you have was the cutting edge of technology in 1958. There is a whole list of "perks" if you will to each tube listed. This one is "light weight, extremely short, 1 1/8" gun diameter, no ion trap etc. The descriptions remind me of those really shallow sets I used to see quite often in smaller homes when I was a kid. Heck, it didn't look like there was more than a foot and a half or so of cabinet top. They looked to be from the early 60s and were always black and white. Sort of odd looking frankly. They were marketed I believe as "space savers." They did do that, but often looked easy (and tempting) to topple over.