Copper came into use in the Aegean area near the end of the predynastic age of Egypt about 3500 BC. The earliest known implement is a flat celt, which was found on a Neolithic house-floor in the central court of the palace of Knossos in Crete, and is regarded as an Egyptian product. Bronze was not generally used until a thousand years or more later. Its first appearance is probably in the celts and dagger-blades of the Second City of Troy, where it is already the standard alloy of 10% tin. It was not established in Crete until the beginning of the Middle Minoan age (MMI, c. 2000 BC). The Copper Age began in northern Greece and Italy c. 2500 BC, much later than in Crete and Anatolia, and the mature Italian Bronze Age of Terremare culture coincided in time with the Late Aegean (Mycenaean) civilisation (1600–1000 BC). The original sources both of tin and copper in these regions are unknown.