A Head Full of Electric Magic

Pop. Mech. April 1929 [big version here]

Two heads really are better than one - even with differing amounts of hair on them.

Use the 1920s miracle hair-growth technique, Dermo-Ray. to grow a new crop of hair, and not only will you have a new look - you'll be able to see and interact with your former bald self.

You will, however, have to use "the electric magic of  infra-red rays" on your head. So you will need electricity in your home. You know, so that you can plug your scalp in and heat it up with infra-red rays. Apparently this was discovered by a nameless surgeon. How did he find this out? By chance, or was he cooking his scalp? I do not really want to know, but it is rather mysterious.

Popular Mechanics, July 1928

Anyway, just send for the Dermo-Ray device (which is, disturbingly, not pictured). And in no time at all ("within a few weeks" - anything from 2 weeks to a year or more, in other words) you will have lots of new hair. And a very hot scalp, too; you can chuck all the fedoras in your closet for good. Three cheers for the Larson Institute of Chicago!* It's just too bad that these guys - all four heads - do not look happier. You'd think the After Head would look a little perkier, wouldn't you?

*Where else? Of course this place is in Chicago - because back in the early 20th century Chicago was the (unofficial) world capital of all sorts of astonishing novelties and inventions. Just click that tag "Retro Chicago" if you want to be totally amazed and entertained by more of them.