Some place I have a Beta video I made of a skinny teenage nerd kid (me), lining up a bunch of CRTs, including a 21FB and several 21FJs, and a Magnavox 27" B&W one, and throwing an anvil at the sides of them to see how big a kaboom they'd make. If I can find it, I'll post it on the condition I won't get booted out of AK
Looking back regretfully today, they were all good tubes. I just kept getting so many of them, and they were worthless (as were the TVs they belonged to). Also at that time (1980-ish), a 21" round color tube was $39, and any B&W tube (except electrostatic) was $16.95 out the door from any rebuilder. So therewith I plead not guilty. I also used to put roundie color sets out for the trash man, and help him heave them into the crusher. I'd put a gentlemens' bet on how many seconds until the KABOOM would be heard inside the truck. Those were the days...
Charles