Michael Gallon, 49, found the coin near Fortrose in Ross-Shire, in the middle of a field.
The soil had recently been turned over, and the coin was sat on the surface, he explained.
He took the coin back to his van to study it in more detail, and noticed it was an 1807 quart franc.
The coin shows the head of Napoleon on one side, and a wreath surrounds the word ‘quart’ on the other.
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