19th century Japanese flip-over drawings

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Pink Tentacle has a nice gallery of old Japanese drawings of heads that look like faces right-side-up or up-side-down.

Joge-e, or “two-way pictures,” are a type of woodblock print that can be viewed either rightside-up or upside-down. Large numbers of these playful prints were produced for mass consumption in the 19th century, and they commonly featured bizarre faces of deities, monsters or historical figures (including some from China). Only a few examples of original joge-e survive today.
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