Construction crews have been working hard to renovate Detroit’s Michigan Central Station in order to turn it into Ford’s technology headquarters. The building, finished in 1913, has proven to be a trove of small, historical treasures, though.

The latest such historical knick-knack is a pre-prohibition era Stroh’s beer bottle stuffed with a letter. Unfortunately, although the message was removed by Ford archivists, they’re struggling to read the contents of the letter.

The message is suspected to have been written by a construction worker, who apparently wasn’t too worried about drinking on the job, and was found by two workers called Lukas Nielsen and Leo Kimble earlier this month. The bottle, curiously, was found high up in a high section of plaster in the station’s tea room. Fortunately, they were restrained enough to leave the message in the bottle.

“It was extremely tempting, it really was,” said Nielsen. “If we did anything to remove it, we would have destroyed it.”

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The pair have found other vintage bottles in the station, but never one with a letter rolled up inside. In all, teams working in the station have discovered 200 items including a saucer from a china set, baby shoes, women’s shoes, adding machines, payment ledgers, and a Shinola shoeshine bottle, among others.

More than 100 items, says Ford, have been used to recreate new versions that will find a home in the renovated building, whose Beaux-Arts style is being maintained to keep a link to the past.

As for the letter, the next step for the archivists is to preserve it.

“The main thing you have to do is slow down the deterioration of the paper,” said Heritage and Brand Manager Ted Ryan. “With the bottle, that’s easy because it’s glass, but we’ll also have to make sure the rest of the label doesn’t deteriorate. It’s just like the pieces of a classic car.”