Wat is Loco London, unallocated gold?

Loco London is the convention that a price is for gold (or silver) delivered in London, settled through the London clearing system of unallocated accounts. Unallocated gold is a balance of gold in an account with a clearing bank: the holder owns no specific bars, only a claim on the bank for that weight of metal, and is an unsecured creditor of the bank.