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Caution

Cone Stamp

The U.S. 2-cent issue honoring Charles D. Scanlon, inventor of the traffic cone, who got the idea and created a prototype in 1940 while working for the Street Painting Department in Los Angeles. The U.S. patent for his invention was applied for in 1941 and granted in 1943.

(You might read on the Internet that the first traffic cone was invented in 1914, 1915 or 1918 by Charles P. Rudabaker/Rudebaker of New York City, and was originally made of concrete, a block of concrete, or a wooden pyramid. However, there is no U.S. patent at that time, under either name. Searches of a New York newspaper database of more than 25 million pages and of Ancestry.com find no Charles Rudabaker/Rudebaker. A Google search finds 200+ mentions, but none before 2006, and none citing a source. Charles Rudabaker/Rudebaker appears to be fictional.)

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Utility

The creation of the Universal Postal Union spurred a competition among those countries that thought their postage stamps could be more beautiful, and, in fact, actually do more than those of other nations.

Dial Pressure Stamp

This Haitian 5-centime measured the p.s.i. inside an envelope to warn recipients of contents packed under pressure.

Dial Norton Stamp

Another cautionary issue, the Netherlands’ 5-gulden stamp indicated the voltage of a letter, using the classic Norton Voltmeter.

Dial Compass Stamp

The New Zealand 4-pence included a working compass for those traveling with the mail.

Dial Radio Stamp

The Malta 2-pence “Silvertone” brought in radio stations from all over the world.

Dial Safe Stamp

The short-lived U.S. 10-cent “Safe Lock” stamp offered remarkable security, but unfortunately senders often included the necessary combination inside the letter, thus locking out the recipient who had to visit either the Post Office or a locksmith to gain access.