One of Bidder’s bottles (Photo: Marine Biological Association of the U.K/Facebook)

A few months back, Marianne Winkler and her husband, Horst, were taking a vacation on Amrum, a German island in the North Sea, just south of the border with Denmark. She was walking along the beach one day, when she found an old bottle. Inside, there was a note with instructions: Break the bottle.

Marianne tried to retrieve the bottle’s contents without breaking it, but it was impossible. So, she and her husband broke the bottle, the Telegraph reports. Inside, they found another piece of paper—a postcard with instructions to send it back to the Marine Biological Association of the U.K. So they did.

Starting in 1904, 111 years ago, George Parker Bidder, marine biologist interested in geology, erosion and sponges, released 1020 of bottles just like the one Winkler found into the sea. His aim was to better understand how the deep currents of the sea worked: the bottles were designed so that they’d bob along close to the sea floor.

Most of them were found in the months after their release, by fisherman trawling deep in the water. And with the evidence he collected, Bidder was able to show these deep ocean currents moved from east to west.

The Marine Biological Association of the U.K. believes that the bottle Winkler found was released in the latter part of the experiment, in 1906. That would make it 108 years old—and, most likely, the oldest message in a bottle ever to be recovered to date. The final determination is now being put in the hands of Guinness World Records.

The association also made good on Bidder’s promise of a reward to anyone who found the bottle and returned the postcard—one shilling.

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