This is a “Biscuit” which is a bundle of at least one coin found at a shipwreck that has been cocooned in oxidation and shells. This particular biscuit is guaranteed to contain at least one Dutch Rider Ducatoon. It was recovered from the Vliegenthart shipwreck which sunk in 1735 off the coast of Zeeland, Netherlands.
The “Biscuit” measures to be 54mm by 49mm