EUROPE : San Marino Joins World <i> Con Brio </i> : U.N. welcomes the mouse that soared. Castles outnumber fast-food outlets in oldest republic.

The mountain wind bites cold, streets built for summer tourists are deserted, many shops are closed and the government is in crisis. Still, it is a golden moment for the world’s oldest republic.

San Marino is the mouse that soared: an Italy-surrounded nation that boasts one bookstore, two fast-food restaurants, three mountaintop castles, four jail cells, usually empty, and a world-class crossbow team. You can call a taxi any time--between April and October.

By acclamation this week, the United Nations General Assembly formally welcomed 23-square-mile San Marino, population 23,609, as a full-fledged member of the world body.

For San Marino, a rocky speck in the northeast of the Italian peninsula, U.N. membership--accorded the same day to eight newly independent Soviet republics--represents the final stamp of approval in a 17-century quest for international acceptance. San Marino brings both symbolism and substance to an organization dedicated to peace: The last homicide here happened in the 1970s, when a jealous husband killed his wife and her sister.

“We may have something to say to the world. We have asserted independence for 1,700 years, and in that time we’ve never had a war, never attacked anybody,” said Clelio Galassi, the minister of finance in a coalition government that collapsed last month.

Dominant Christian Democrats will likely join Socialists in a new government for a country whose people, thanks to 3 million tourists a year, are as well off economically as the Italians in neighboring Emilia-Romagna, one of Italy’s richest regions. Light industry and the international sale of postage stamps combine with the tourists to support a cradle-to-grave social welfare system that is a prideful hallmark of a singular nationalism.

The people of San Marino speak Italian, watch Italian TV, read Italian newspapers and go to Italian universities but insist they are something else.

“People talk about ‘going to Italy.’ It’s a different place,” said Pier Roberto de Biagi, a spokesman for the vest-pocket Foreign Ministry. “We are not Italian, but Sanmarinese. We have our own history; we belong to our own country. We have our own laws. We even have two heads of state.” Since 1243, San Marino has been a republic in which a 60-seat National Assembly elects two of its members to rule as coequal captain-regents for six months.

In context, San Marino is the long shot that came home, the little guy who couldn’t survive but did. The official date for its founding is Feb. 3, 301, the inspiration of a holy man stone cutter named Marino who became a saint. The national territory hasn’t varied one inch since 1463. Unlike all the other small states that once dotted Italy, San Marino never fell to an invader, an acquisitive Pope--or even a dominant family.

“At first we were favored by remoteness and a lack of strategic importance--an island not worth disturbing. That took care of the first thousand years. Later, we survived as a useful buffer state between powerful rivals of north and south,” said Marino Cecchetti, a school principal and historian.

In many ways, San Marino’s history is more compelling than the tinsel of its tourist-driven present. But its spunk and its sere beauty on the slopes of Mt. Titan in sight of the Adriatic have long attracted international admirers: Abraham Lincoln, whose letter praising San Marino’s republican principles is a gem of the national archives; Napoleon, who offered to expand the republic but was rebuffed by its citizens; Giuseppe Garibaldi, the father of modern Italy, who sheltered here during one bleak spell, and the founders of the Los Angeles suburb of San Marino, who borrowed the name, and the official shield, from the doughty mountain republic.

Italy long kept San Marino on a tight leash. Today, as ever, its well-being depends on Italian goodwill. The republic opened its first embassy, in Rome, only in 1979. In the decisive 1980s though, San Marino joined the Conference on Security and Cooperation in Europe and the Council of Europe.

Now that the U.N. flag flies alongside the republic’s historic blue and white national insignia, the Sanmarinese are already preparing for their mighty mouse’s next flight: membership in the International Monetary Fund.