Coin used by spies to hide messages during the Hungarian War of Independence (1848-49).
Fullsize image: https://s3-us-west-1.amazonaws.com/h...n_fullsize.jpg
Previously:
Hobo nickels: intricate carvings in coins - GIF and photos
Coin countertop - photo
Polishing a tarnished coin - GIF
Squeeze coin pouch - GIF
Mosaic murrini glass coin - GIF
How to make a coin ring - GIF
Folding coin knife - GIF
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