The London bullion market is a wholesale over-the-counter market for the trading of gold, silver, platinum and palladium. Trading is conducted amongst members of the London Bullion Market Association (LBMA), tightly overseen by the Bank of England. Most of the members are major international banks or bullion dealers and refiners.
The physical characteristics of gold and silver bars used in settlement in market is described by the Good Delivery specification which is a set of rules issued by the LBMA. It also puts forth requirements for listing on the LBMA Good Delivery List of approved refineries.