by Stephen Beech An ultra rare Aussie coin found in a charity shop is expected to sell for thousands of pounds at an auction next week. The early 19th Century 15 pence piece – known as a “Dump” – was spotted by Oxfam volunteer John Turner while looking through a bag of coins that had been donated to the charity’s store in Orpington. The coin identified as a rarity by former banker Mr Turner, who is in his mid 70s and has volunteered for Oxfam for the past 10 years since retiring, was taken to Noonans Mayfair auction house in central London for a second opinion. Experts confirmed it was an Aust…