Call it art. (It is perhaps the most accessible art form.) Call it a hobby. (According to the American Philatelic Society, it's the world's most popular one.) Call it a form of social commentary. (What a diverse display of cultural values.) FIGURES 1-14

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In the last 150 years, more than 700 entities-nations, provinces, cities, and armies-have issued postage stamps. And unlike anything except currency, they're marked with a monetary value by the source that issues them. Intricate stratagems have been devised to prevent the counterfeiting of stamps-they have been embossed, watermarked, and microprinted, and their perforation holes have been precisely spaced. Chemically treated stamps trigger sensitive devices in mail-sorting machinery. And the hologram has three-dimensionally enhanced their images.

Stamps are special to us. Postal authorities work hard to secure their authenticity, and cultures strive to select representative images and subjects. Here are some philatelically celebrated nursing images.