A 1666 Norwegian coin recently was auctioned off at the Heritage Auctions' World Coins Signature Auction in Chicago. The coin depicts Frederik III who ruled Norway and Denmark from 1648 to 1670. The coin was sold for a whopping $432,000 which is far beyond what it was expected to go for. This is due to the fact that there are only 3 examples of this coin known to man with the last auction for this coin happening over 200 years ago.
This particular coin was graded by NGC as VF DETAILS with writing on the reverse side of the coin. The writing appears to say "JEN" and "PHAM". It is unclear as to what these words mean, but some have speculated that it is someone's name. This graffiti is only visible from a certain angle of lighting.