The ".999 Fine Silver Enriched" means that this is not pure silver, but has a heavy silver content. The purity rate for silver bars and rounds is much the same, but they come in 3 typical forms other than jewelry or forks and spoons.
Bars and rounds at .999 fine is a higher grade of purity than collectible silver coins, which are typically 90% fine or .900, or sterling silver, which is 92.5% fine or .925.
Recently this year, a record-breaking 48 tons of silver bullion have been recovered from the SS Gairsoppa, a World War II shipwreck, three miles beneath the ocean's surface. Odyssey Marine Exploration, a leader in deep-ocean shipwreck exploration said their initial retrieval effort yielded 1,203 silver bars (merely 20 percent of the total silver cargo estimated to be on board).