Before you sell that silver dollar or those baseball cards, you might want to check with Collectors Universe. The company provides authentication, grading, and information services for sellers and buyers of trading cards, event tickets, vintage autographs, and other memorabilia. The company charges a fee -- usually between $4 and $200 per item -- to determine the authenticity, quality, and worth of the collectible. Coins and sports cards account for most of the company's business; notable offerings include its Professional Coin Grading Service (PCGS). Collectors Universe also publishes price guides, market reports, rarity reports, and other information in print form, as well as on its website.