Alll the stories on radiation and polonium-210 got me to thinking about the design of the radiation warning symbol.
Here it is:
The three-bladed radiation warning symbol, as we currently know it, was "doodled" out at the University of California Radiation Laboratory in Berkeley sometime in 1946 by a small group of people. This event was described in a letter written in 1952 by Nels Garden, head of the Health Chemistry Group at the Radiation Laboratory: "A number of people in the group took an interest in suggesting different motifs, and the one arousing the most interest was a design which was supposed to represent activity radiating from an atom."
The first signs printed at Berkeley had a magenta (Martin Senour Roman Violet No. 2225) symbol on a blue background. In an earlier letter written in 1948, Garden explained why this particular shade of magenta color was selected: "it was distinctive and did not conflict with any color code that we were familiar with. Another factor in its favor was its cost. . . The high cost will deter others from using this color promiscuously." Explaining the blue background, he said, "The use of a blue background was selected because there is very little blue color used in most of the areas where radioactive work would be carried out."
Garden did not like yellow as a background: "the very fact that . . . the high visibility yellow stands out most prominently has led to extensive use of this color and it is very common." To compensate for the lower visibility of the blue, Garden even toyed with the idea of including diagonal white stripes across the sign.
From: Origin of the Radiation Warning Symbol (Trefoil).
And here is Jimmy Page with a warning for all you love weary Russian spies: