Secondary market popularity of an America the Beautiful 5-oz. silver bullion coin is difficult to predict; mintage is only one factor in higher premiums.

Some lots offered in online auctions virtually guarantee a bidder will lose money by placing almost any bid.

Sometimes the online auction experience can cause consternation.

Half dollars: A mysterious rarity

The eighth known, second finest 1817/4 half dollar, an ultra-rarity, was found in a load of fill dirt; now 11 are known. It last sold at auction for $164,500.

A preview of some forthcoming issues recently heard about, by no means comprehensive.

Celestial Dome series concludes with Northern Sky coin

Besides being often counterfeited, many $3 coins were damaged by being mounted in jewelry, another good reason to shop only for reliably certified examples.

A 1-ounce silver round can cost much more than it's worth if you don't check around but agree to an auctioneer's terms, high price and high delivery charges.

U.S. Mint experiments with platinum for coinage produced some odd coins, including an 1814 half dollar that looks normal, but for the 33 Ps punched on its face.