After a community group in Shropshire, England, decided to have a donated piano tuned, the tuner made an incredible discovery. Inside the upright piano, first sold in 1906, there was a hidden stash of gold.

The group immediately reported the find to authorities, and the gold has been taken to the British Museum. Authorities aren’t giving out details about what exactly was found, but it’s supposed to be “highly unusual in nature” and “made mostly of gold.” (One source mentions coins.) Whatever it is, it is apparently remarkable.

“They laid this stuff out and I was like ‘whoa’, I’m an archaeologist and I’m used to dealing with treasure but I’m more used to medieval broaches,” the British Museum’s Peter Reavill told reporters.

The United Kingdom actually has a law to deal with discoveries like these, the Treasure Act of 1996. For the hidden gold to officially be declared treasure, “it must be substantially made of gold or silver and have been deliberately concealed by the owner with a view to later recovery,” the Shropshire Star reports.

If the original owner is not found and the hoard is declared treasure, then it will belong to the Crown. The museum will be able to buy it, and the tuner and the piano owners will get a reward—a finder’s fee, essentially. But authorities are still trying to trace the piano’s ownership history and find the original owners of the gold. If they do, perhaps we’ll find out what exactly is in this giant pile of gold—and why it was hidden in the first place.