Well-kept secret?

[Electronic M]

After the war TVs were still expensive, and many tubes were in short supply so if it was avaliable, cheap, and could do the job in it went.

[David Roper]

Originally Posted by Electronic M

After the war TVs were still expensive, and many tubes were in short supply so if it was avaliable, cheap, and could do the job in it went.

There's more to it than that though. There are some eccentric designs lurking in old service literature, such as sets for use on 110 volts DC. Sometimes it's fun just to browse old Rider volumes like one would a catalog just to see how creative the engineers could be.