Your item may sell or it may not. And if it sells it may sell for a fraction of what it's worth. And the auction house takes a percentage of the selling price, which could be up to 25%. You can put a reserve of the item, which means you don't have to sell the item unless the bidding reaches a reserve price. However if the reserve price isn't met, and doesn't sell, you still owe the auction house the seller's fee on the reserve price.
You take your items in and they put it in one of their upcoming auctions. They keep a percentage of the sale and you get a check for the rest in the mail. I'd suggest going to a jeweler who buys silver and you will make out better if it's real silver and not stainless or silverplate.
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