Ask what they'll buy it back for

A woman came to me wanting to sell gold coins she'd bought years earlier as an investment. Here's the thing about anything sold to you as an investment that you can hold in your hand: coins, collectibles, memorabilia. There are two prices: what a dealer will sell it to you for, and what a dealer will pay you for it. The gap between them can be enormous, and nobody volunteers it at the point of sale. Before you buy, ask the salesperson one question: what would you pay me for this if I walked in with it tomorrow? If they won't give you a number, that's your answer.