As an aside, old pennies were made of pure copper and were three to the ounce. Once the price of copper got to £600 a ton then it was worth melting them down. As a schoolkid I went on a visit to Enfield Rolling Mills to see the stuff being smelted and worked which was quite an experience. On one occasion there was a lorry parked just inside the entrance with billets of pure copper and brass, these were about 1 metre square by 15cm thick, and somebody just walked in a drove off with the lot, lorry and all.