The Good Delivery specification is a series of rules published by the LBMA (London Bullion Market Association) that defines and regulates the requirements for gold and silver bars. 

These internationally recognised standards set the benchmark and ensure that accredited refiners maintain the necessary high standards required for inclusion in the London Good Delivery Lists.

If a refiner no longer meets these requirements or chooses to stop manufacturing Good Delivery Bars, they are removed from the list. 

The required specifications for Good Delivery bars cover acceptable weight, purity and overall appearance, including surface quality and markings.