THE GOLD BUG has returned to Great Britain. The Royal Mint is returning to the bullion trade with a 22-karat coin called "The Britannia."

In Western Europe, as in America, sanctions against additional imports of the widely held South African Krugerrand have created a void in the booming bullion market, and the United Kingdom has decided once again to enter the fray.

Jeremy Gerhard, deputy master and chief executive of the Royal Mint, notes that Britain once made the gold coin that was the world standard. He was referring to 22-karat coins minted under a 1634 act of Parliament. "Crown gold" subsequently became the measure by which other coins were judged.

Until the late 1960s, the United Kingdom's sovereign, containing .2354 ounces of gold, was the most widely held of the world's bullion coins. In 1967, South Africa introduced its Krugerrand and took control of the coin market. Since then a number of other nations have followed, including the United States with its Gold Eagle.

The Mint is hoping to win up to 5 percent of the world market.

The coins went on sale in London last week in four denominations ranging from a one-ounce coin (34.050 grams) with a face value of 100 pounds, to a one-tenth of an ounce "Baby Britannia" (3.412 grams) with a 10-pound value.

The mint said the bullion coins will be sold through North American precious-metal dealers at the market price of gold, plus a "small, competitive premium."

It did, however, announce prices for a small number of proof "frosted gold" coins that are being sold to collectors through Barclays Bank of New York. A set of four coins will go for $2,140.

The individual coins and their proof prices include the 100-pound coin for $875; a half-ounce, 50-pound coin for $450; a one-quarter ounce, 25-pound coin for $245; and a 10-pound coin for $100.

The coins carry the standing figure of "an elegant and enlivened Britannia . . . very much a woman of the times," the Royal Mint said. On the obverse is an effigy of Queen Elizabeth II.

Other than the finish, the major difference between the proof and the bullion coin is that the name of the coin's designer, Phillip Nathan, appears as "P. Nathan" on the proof and as "Nathan" on the bullion.

Gold isn't the only collectible whose price is soaring. The Associated Press says Coach Investments Inc. of New York has set a record for sale of a single stamp.

The firm reported that a two-cent "Lady McGill," a mint stamp issued by a private Pittsburg postal service in 1852, sold for $1.1 million to an anonymous collector.

The previous record was $1 million, which the Guinness Book of World Records says was paid in 1981 for a 5-cent "Blue Alexandria" cover issued November 25, 1846, in that Northern Virginia city.

Marc Russo, chairman of Coach, said the "Lady McGill" surfaced only seven years ago when it was described in a 1980 publication.

The United Nations will issue a set of six stamps on November 20 to encourage childhood immunizations. To be issued in pairs in New York, Geneva and Vienna, the stamps each promote a particular immunization that the World Health Organization has urged for children.

The two stamps to be issued in New York are a 22-cent stamp urging measles innoculation and a 44-center promoting tetanus shots. The Geneva stamps, a .90 Swiss franc and a 1.7 franc, promote the DPT (pertussis) vaccine and the tuberculosis (BCG) vaccine. The Vienna stamps, a four schilling and a 9.50 schilling stamp, promote the polio and diphtheria vaccines.

The stamps are available from the U.N. Postal Administration, United Nations, New York NY 10017.

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