These pyritized brachiopods (Paraspirifer bownockeri) are from the famous Sylvania Quarry in Ohio, USA. This quarry is now closed and these fossils are very difficult to come across. They date back to the Middle Devonian - 345 to 395 million years ago.
Note: The brachiopods were manually positioned on the slab of matrix. Dimensions: 18 inches x 9.5 inches x 1 inch weight = 7kg.
Learn more about pyritization of fossils