Gold Bars, Good Delivery, and the Professional Gold Market
•The most competitive gold prices in the world, the ones you see published in the papers and on the internet, are enjoyed by the participants in the professional bullion market:- gold dealers, refiners, government agencies, bullion banks and the occasional big investment organization.
•This professional market only deals in what are known as Good Delivery bars. If you're not trading these bars you are excluded, both from their market and from their very competitive prices, which means you'll pay more when you buy and receive less when you sell.
Fine gold is 100% pure gold
•Good Delivery bars are cast by a small group of precious metal refiners accredited by the professional bullion dealing communities in London, New York and Zurich. They are accurately assayed and guaranteed always 99.5% pure gold or better. The market trades their pure gold content (gross bar weight x purity) which is known as fine gold, so no-one who trades professional market bullion ever pays for impurities.
Quoted from: BullionVault.com