IF A MISPRINTED U.S. stamp can sell for $50,000, what's a misprinted dollar bill worth?

Both are printed under the same strict security and scrutiny by the Bureau of Engraving and Printing at its 14th Street plant.

So when Brian Sullivan of Charlottesville discovered a dollar bill with the serial numbers printed upside down, he was convinced that, like the CIA employes who discovered 86 stamps with a candlestick printed upside down, he was on to something big.

But the sad news for Sullivan is that, when it comes to errors, misprinted currency isn't in the same league with misprinted stamps.

Nonetheless, the error Sullivan spotted is considered a genuine misprint and could make his dollar worth as much as $100, according to Donald Frederick of Capitol Coin and Stamp Co. in Washington.

The key to the value of such a bill is its condition, with an uncirculated one bringing the top price. As Frederick puts it: "The nicer it is; the higher it goes."

The latest word on those misprinted stamps, the $1 stamps with the inverted candlesticks, is that their value also is going higher.

Last week, shortly after the disclosure that a group of CIA workers had sold 86 of the stamps to a New Jersey dealer for an undisclosed sum, 18 of the misprints were sold to John Reznikoff of Stamford, Connecticut for $900,000.

That's well above the previously reported top sales price of $17,600 for one of the stamps, but still below $115,000, the catalogue price of the famous inverted 24-cent airmail stamps, the ones with the upside-down airplane.

Many experts have said they expect the candlestick stamps will soar to that level, if the other 305 misprinted candlestick stamps that must have rolled off the bureau's presses at the same time don't show up.

The unrest in South Korea may have raised questions as to whether the 1988 Olympics will be played as scheduled in Seoul, but the South Korean government is continuing with its elaborate plans for four sets of commemorative coins to help finance the games.

Officials of the Korean Security Printing and Minting Corp. recently went to Atlanta to unveil the coins in their second series to members of the American Numismatic Association. In the process they put in a plug that sales of their coins in the U.S. will help American athletes, since the U.S. Olympic Committee is to receive a sum equal to three percent of the value of the metal in the coins sold to Americans.

The second series includes six coins: a one-ounce gold showing the Grand South Gate in Seoul; a half-ounce gold showing a Korean dancer; a one-ounce silver showing a volleyball player; a half-ounce silver of the Olympic Stadium; a one-ounce silver showing an archer; and a half-ounce silver showing Jeki Cha Ki, a shuttlecock game unique to Korea. All the coins will have a common reverse, depicting roses of Sharon, Korea's national flower.

Manfra, Tordella & Brookes Inc. of New York, the U.S. agent for the coins, is selling the full set in proof quality for $1,345. The two gold coins are being offered separately for $1,250 and the four silver coins for $115. The agents have authorized American Express to sell all of the coins, except the one-ounce gold, in brilliant uncirculated condition, for $549.

The U.S. Postal Service has announced the design for a postcard to commemorate the 50th anniversary of Timberline Lodge, the massive ski lodge on Oregon's Mt. Hood that was built by the Works Progess Administration during the Great Depression.

The card is part of a series that celebrates American architecture. Previous cards featured Utah's Salt Lake Temple, California's Dominguez Adobe and the District's Old Post Office Building.

The principal difference between the Timberline card and its predecessors is that the new 14-cent card is printed on the Government Printing Office's new five-color presses and on a much whiter stock. The new card is part of the GPO's effort to produce postcards as vivid as any U.S. stamps.

Collectors have until October 28 to request first-day cancellations from Timberline Lodge Postal Card, Postmaster, Timberline OR 97028-9992 at 14 cents each. Collectors should provide a peelable return label.

Individuals may mail the cards to: Customer-Provided Cards, Postmaster, Timberline OR 97028-9991 for cancellation.

Bill McAllister is a member of The Post's national staff.