Idiot fishtankers have a website.

[David Roper]

An article written for potential fish-tankers states almost incidentally:

TV tubes up until about 1960 do not have integral implosion protection. These can be extremely dangerous, because they can implode very violently. You'll notice a label on all tubes that are less volatile that says something like, "This tube provides integral implosion protection." If you don't see that, don't mess with it.

This would eliminate from their consideration virtually all sets of any real interest or value to serious collectors.