AUDIE CORNISH, HOST:

Marianne Winkler came away with quite a souvenir during her vacation this year on the North Sea - a bottle. And inside, some instructions that could be seen through the glass, reading, break the bottle. It may be the oldest message in a bottle ever found. It was dropped into the North Sea sometime between 1904 and 1906 by the Marine Biological Association of the United Kingdom. And joining us now from Plymouth, England, is the MBA's Guy Baker. Welcome to the program.

GUY BAKER: Thank you for having me.

CORNISH: What was going through your mind when you got word word that Marianne Winkler, this retired post office worker, had found this bottle?

BAKER: Well, we received a letter, and it was addressed to G.P. Bidder. And he hasn't worked at the MBA for a long time. And so we thought, OK, what's this? And we had a look inside, and we found this rather old undamaged but old-looking postcard, and we thought, this looks interesting. And we went into the archives, and we found other similar postcards returned from the northeast coast of England and from Germany and from Denmark.

And with a little bit of research, we saw that this was indeed one of the postcards that was inside a bottle that had been released in 1906. It had either been buried in the sand on the beach or knocking around the sea for a long time. So we don't really know what had happened to it in the intervening 108 years, but it was exciting. Nothing like this has happened in living memory.

CORNISH: And you mentioned G.P. Bidder. Talk about who he was. He's the man behind this project, right?

BAKER: That's right. George Parker Bidder was a scientist, and he worked at the Marine Biological Association in the early years of the 1900s. He was very interested in the currents in the North Sea and how they related to commercial fish. So he had to invent a piece of scientific equipment. And with the technology available at the time, he came up with what he called a bottom bottle. And this was glass bottle about the size of a beer bottle - very well stoppered, waterproof. And it was weighted with lead shot so that it would float neck-down.

When these bottles were thrown into the sea, they'd trail along just above the bottom, and the idea was that they were picked up by fishermen who were fishing for bottom-living species. There were instructions on the postcard about what to do with it and questions such as, where did you trawl up the bottle? How deep was the water? What was the time - and so on. And that way, they'd get the information back so it was sort of a early form of citizen science, really.

CORNISH: There was a reward included as well - right? - a reward of a shilling promised if the postcard was returned. Have you made good on that promise to Miss Marianne Winkler?

BAKER: Yes, we did. We honored the promise on the card. One shilling was promised to the fishermen or the finders of these bottles. And we went on eBay, and we found an old shilling.

CORNISH: Because they're not minted anymore, right?

BAKER: No, no.

CORNISH: (Laughter) They stopped making shillings in 1970, so I don't know.

BAKER: It was an old shilling, and so we sent her her reward.

CORNISH: Now, this is the oldest one you guys have believed to have gotten back so far, but there's still a chance people could find more, right? I mean, there are unaccounted-for bottles.

BAKER: That's right. We've got 599 of the original 1,020 returned. The longest one recorded at sea in the original research was nearly four years at sea, so 1,434 days. That was the last one that was recorded in the archive as part of the original experiment, but we haven't had another one back in living memory. So this one turning up, it means it's not impossible that one of the other ones could turn up. There's still over 400 unaccounted for. I think it's very unlikely, but you never know.

CORNISH: You didn't buy an extra shilling, did you?

BAKER: No, we didn't.

CORNISH: Guy Baker - he's from the Marine Biological Association of the United Kingdom. Thank you so much for speaking with us.

BAKER: Thank you very much. Transcript provided by NPR, Copyright NPR.