Radio was booming in the 1930s and retailers were looking for every way possible to sell more sets.

Here are some marketing tips from the American trade magazine Radio Today:

That's worse than today's teenager with a mobile phone that is more than 6 months old.

Considering for many working people a radio purchase was perhaps a years wages I don't know how they could put that over.

Many people of that era I have spoken to kept their radios running for at least 15 years.

Must have been desperate for sales to try and put that one on.

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I've been reading quite a bit about those boom days of radio. Americans were buying radios at unprecedented rates in the late 1930's as the US economy began to recover from the Depression, and WW2 wasn't yet on the radar. Manufacturers and distributors were pushing sets onto the retailers, with new features every year plus 'facelift' models -- a trick that the car industry hadn't yet cottoned onto.

Middle class Americans were cashed up and confident. The number of sets made and sold each year in that era was astounding. Some of the big manufacturers were boasting of shipping 200 rail cars full of new sets.

There was even an industry-agreed rate card for trade-in prices of mantels and consoles.

Another trick was advertising that valves got tired and that sets needed to be checked out for such things.

Another trick was advertising that valves got tired and that sets needed to be checked out for such things

And here we are 80 years later and valves are the most reliable part of the set.

It was a racket. Valve manufacturers were cranking them out by the bazillion against an unknown demand, so they created a demand by such advertising. Some manufacturers stocked radio dealers on consignment so they carried their full line at zero holding cost.

Dealers also had DIY valve testers -- basically shorts and emissions testing with Good/Bad scales -- so that customers could test their own tubes.

Manufacturers like Ken-Rad published facsimiles of 'customer letters' which said that sensitivity and tone had increased greatly since they fitted that brand.

In Germany, they had this trick:

Another racket of the era was the '14 Tube' set. Some shady manufacturers were producing and heavily plugging 14 valve sets wherein 8 or 9 of those so-called valves were ballast tubes.

Something I forgot to mention earlier, throughout the whole of the valve manufacturing era there was cross manufacturing by valve makers.

Production lines became overloaded making certain types of valves so a manufacturer contracted another valve maker to make batches of valves for them.

A KenRad could well have been made by Philco. Mullard valves could have been made by Philips at their Holland plant. Or vice versa.

In this era, on the audiophile scene there are so called experts whom have great discussions on how to identify for sure certain types of sought after rare audio valves.

Fakes abounded everywhere even in the days gone past and nowadays the Chinese are past masters of the art of faking valves.

Read an article written by a well known German audio supplier whom went to China to get batches of valves made for his sales line.

The Chinese asked him quite openly what brand name did he want to have printed on the valves!

Given the rarity of some valves I would not care what brand it has - only that it must work.