A village in northwestern France is offering 2,000 euros ($2,200 USD) as a reward for deciphering a strange secret code which was found carved into a small boulder found on a beach. What could be hidden in this message?

The boulder was found along the shores of Plougastel-Daoulas, a village of about 13,000 people in a bay on France’s northwest peninsula. The stone was discovered a few years ago and is only visible at low tide and is covered in a mysterious encryption of jumbled capital letters and crude symbols carved into one of its faces. Some of the symbols appear to depict a sailboat and a heart, while others are less easy to make out.

According to French news site France 24, locals compare the rock to the Rosetta Stone, although there is some evidence that it may be related to France’s military history. There are two dates legible on the stone, 1786 and 1787, which correspond with the construction of nearby artillery batteries built to defend a nearby fort.

Village authorities and nearby scholars have examined the rock, but so far no one has been able to decipher the inscription. One legible section reads “grocar drear diozeevbio.” Some believe it may have been written in a form of the Basque language, while others think it may be an older form of Breton. “There are a lot of words, they’re letters from our alphabet, but we can’t read them, we can’t make them out,” says Michel Paugam, the municipal councilor in charge of local heritage.

The village hopes the offer of the reward could help solve the mystery carved into the stone. A jury will chose among the entries to select the most plausible suggestion and award a prize.