The Schist Disc or Disc of Sabu was found in the tomb of prince Sabu, son of pharaoh Anedjib and can therefore be dated to around 3100-3000 BC.
Many diverse claims have been made for this disc including chemical mixer, seed distributor, sound resonator and ornamental vase.
It is said that he disc has been carved from a single block of brittle schist using only the copper chisels and dolerite mortars that were available to the dynastic Egyptians.
Just looking at the picture though it seems more likely that it is made from metal that has been cut and bent into shape and then given some sort of coating for durability.
This video however, presents a convincing case that the disc is designed as a rope wrench for weaving together the various strands of a rope, or if the disc is too fragile for rope then a similar function for weaving silk.