Coins carved to reveal skulls under the faces

Hobo Nickels are bas relief carvings of coins, and were especially popular during the great depression, when people sold them as novelties.

From Wikipedia:

About 100,000 (and possibly as many as 200,000) classic hobo nickels were created from 1913 to 1980. Modern artists have created (and continue to create) altered nickels in such large quantities that, within the next few years, the number of modern carvings is expected to surpass that of classic old hobo nickels. Most of the 100,000-plus classic old hobo nickels are not yet in the hands of collectors, whereas almost all modern carvings are. Among numismatists, the modern carvings already greatly outnumber the classic old hobo nickels.

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