The question I hear most often at antiques shows is, How do you know whether something is silver? People aren't necessarily looking only for sterling; they just want to know what they're buying. Most of the time, you can find the answer simply by turning over the teaspoon, fish fork, ice cream saw, or cheese scoop (antique flatware is that specialized).

On the reverse side, you usually find an indented mark or series of marks that holds a wealth of information about the item -- not only what it's made of, but sometimes also where, when, and by whom it was made. This applies to hollowware -- such as cups, bowls, teapots, and vases -- too.

The first step in deciphering these marks is to learn what kinds of silver are out there. Some of the oldest American silver is coin, which contains an amount of the precious metal that was set by the U.S. Mint for coinage after the American Revolution: Coin made from 1792 to 1837 is composed of at least 89.2 percent silver and, thereafter, 90 percent.

Sterling, in contrast, must be at least 92.5 percent silver. This standard -- 92.5 parts pure silver to 7.5 parts copper alloy, which strengthens the softer silver -- was established by the English during the 12th century and later adopted by most of the silver-making world, including the United States in 1868

Many people think of coin as much less valuable than sterling, but it has only about 2 percent less silver and, in some cases, may even contain more. Because of its age and beauty, a piece made from coin can sometimes be worth more than American sterling.

Silver plate -- a coating of pure silver on a base metal such as copper or nickel silver, which is actually an alloy of nickel, copper, and zinc -- was a later development. Various forms date to the 18th century. Electroplating processes were invented in England in the 1830s and 1840s; this method is still used. Hotel silver is electroplate that was manufactured for use on trains and steamships and in restaurants and hotels. You can dent a sterling sugar bowl very easily, but a similar piece of hotel silver can be dropped without much harm because the underlying base metal is stronger than silver.

Certain alloys, referred to as Venetian silver and Nevada silver, consist of nickel and silver. Although they're solid metal rather than plated, they contain less silver than sterling does. These lower-grade compounds are often less costly than silver plate but don't polish up as brightly.

The next step is to learn the meaning of the most common silver marks. England's system of hallmarks -- a variety of official emblems stamped on silver to attest to its purity -- is one of the oldest and most detailed. Laws dating to the 14th century established strict requirements for marking silver; the first emblem was a crowned lion's head to certify sterling.

Hallmarks are stamped in a row on all sterling: The lion symbolizes British sterling -- and because its appearance has changed through the years, this hallmark alone can help date a piece. Symbols for the city of origin include an anchor for Birmingham and a crown for Sheffield (since 1975, a rose). Another mark is the head of the reigning monarch. A letter stamp provides the date of manufacture: Each year is assigned one letter of the alphabet; a new cycle starts with a different font. Until the 1500s, the symbol for the silversmith was often a plant or an animal suggesting the family name. Today, initials are used.

American marks weren't enforced as systematically and were therefore never as elaborate. Early coin silver was often marked with the maker's name, and nothing else; sometimes it doesn't show even that. (Unmarked objects, of course, present the greatest mystery.) Eventually, manufacturers also started using the word coin.

With the adoption of the sterling standard after the Civil War, silversmiths continued to stamp their own names on the back, along with the word sterling or the number 92.5 or 925, all of which indicate sterling quality. Some companies used symbols as a commercial logo. The Gorham company's mark was a row of three emblems: a lion (for sterling), an anchor (for its base in Rhode Island), and a "G" (its initial). Some American silversmiths mimicked British hallmarks to lend their wares prestige -- rather than to convey specific information.

Silver plate has its own codes in the United States and abroad. The maker or company name is usually stamped on the back of the piece along with an indication that it's plated: in America, for instance, A1, AA, EP, sterling inlaid, or silver soldered. By industry practice, AA has one-third again as much silver used in the plating as does A1.

Like faux hallmarks, the terms "sterling inlaid" and "silver soldered" attempt to improve their status by association, here, with sterling silver. "Sterling" alone means solid sterling silver; if other words accompany it, beware. Learning to distinguish plate from sterling and American from European silver is a good starting point. Beyond that, you will have to do your homework; even the experts rely on books.

Three volumes cover the most ground for a beginner: Kovels' "American Silver Marks," by Ralph and Terry Kovel (Crown; 1989); "Silver Flatware," by Ian Pickford (Antique Collectors' Club; 1983); and Silverplated Flatware, by Tere Hagan (Schroeder; 1990).

A final tip: It's a good idea to bring a small, cheap jeweler's loupe when you go shopping. I need one for house sales held early in the morning or for those where the tableware has been relegated to a garage illuminated by a single lightbulb. With silver marks, it's a tiny world, so it's best to come prepared.