The watch below is a rather old watch with rusted hands. It still runs. I noticed some funny dark areas on the crystal exactly over the very thickly painted radium hour numbers. I took a Geiger-Muller counter to the watch, and it was loaded with radioactivity. I then laid the watch face down on a sheet of x-ray film in a dark room, left it for a few minutes, and processed the film. To the left is the image pattern created by the radiation field around the watch dial. Taking off the crystal, below left, you can see the brown areas where the radiation has caused accelerated deterioration of the plastic. The last repair date of this watch is 1945.
False-color optical density analysis shows that the crystal spotting is most intense at 10 and 4 o'clock, where the red color is indicated.

Who are those girls seated at the lower left? They are watch dial painters. Radium, a radioacitve substance, was mixed with other ingredients to create a luminous paint for applying to the dials and hands of clocks and watches, making them glow. In the 1920s, young women, most just out of high school, were employed as dial painters at an East-coast company. Apparently the pay was pretty good. In order to paint neat and sharp numbers on the dials, the girls were encouraged to occasionally "sharpen" the fine brushes by using their lips and teeth to straighten the bristles. Naturally, some of the paint was ingested. No one warned them of any potentional harmful effects. In fact, some girls painted their teeth or applied glowing "makeup" as a novelty to show their friends. In the late 1920s, some dentists began to notice a high incidence of jawbone
Radium Watch Dial Pattern
deterioration among young women, most of whom had worked at the dial company. Later, cancers of the head and neck, anemias, and other disorders were found, resulting in some early deaths. Clearly the implication was that the radium paint was directly responsible for the illness. The topic still is controversial, and I don't really know the data from a scientific point of view, but my "gut feeling" is that something bad happened here. A book has been written about the subject, "Radium Girls: Women and Industrial Health Reform," by Claudia Clark. Radium has an interesting history: It was hailed as a miracle discovery, and was used in radiotherapy for certain cancers. It made its way into some cure-all potions, and even into radioactive soft drinks! Radium spas existed, where you were supposed to swim in vats of radioactive water, to cure various ills and improve your health.

I have more recently done some more experiments with a dozen or so 1950s Timex wristwatches. More radioactive dials were found, and x-ray pictures created. They're beautiful in  strange way. Here is the link.

There's more about these radium workers at the Museum of Atomic Permutation click. Here's a great article about an ambitious boy who tried to make a nuclear reactor for a Boy Scout project using chipped paint from old radium-coated clock and watch dials.
Luminescent Watch Dial Page
This is a piece of x-ray film. Black is where radiation existed.
Electron Microscope Pictures of a Watch
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Timex watch dial x-ray patterns