(MONEY Magazine) – By now, you've probably seen former Apollo astronaut Buzz Aldrin on TV hawking those new $5 coins commemorating the 20th anniversary of the first moon walk. The lunar coins, along with their $50 sisters, are issued by -- and are legal tender in -- the Republic of the Marshall Islands, a former U.S. trust territory in the South Pacific. A Cheyenne, Wyo. marketer called Unicover World Trade Corp. sells them by direct mail in the U.S. In his commercial, Aldrin calls the currency ''a reflection of American ingenuity.'' But do the coins reflect any genuine investment value? Don't bank on it. Dealers say a better investment would be the 1973 Eisenhower U.S. silver dollar, which sports the Apollo 11 insignia and now sells for $43. ''Mass-produced commemorative coins from small countries have never proved to be winners,'' says Luis Vigdor, executive vice president of MTB Banking, an international coin dealer. As a rule, the strongest investment market for a coin is its issuer's country, but the Marshall Islands' population is a mere 43,000. In addition, the $50 coin, which sells for face value (plus $6 for handling and insurance), costs far more than the bullion value of its one ounce of silver -- a mere $5. ''I would probably pay only what the silver is worth,'' cautions Gary Adkins, senior numismatist of Premiere Coin Investments in Apple Valley, Minn. And, oh, yes, the $5 moon coin, promoted as nickel-silver, is in fact a nickel-copper-zinc alloy.