Elvira Clain-Stefanelli, 86, a coin scholar who with her husband aggressively expanded the holdings of the Smithsonian Institution's National Numismatic Collection and retired last year as its top official, died of cardiac and pulmonary arrest Oct. 1 at Virginia Hospital Center-Arlington. She lived in Arlington.

Mrs. Clain-Stefanelli joined the Smithsonian in 1957 as an assistant to her husband, numismatics division chief curator Vladimir Clain-Stefanelli. She was promoted to curator in the mid-1960s.

Her husband died in 1982, and two years later, when the coin division became a department, Mrs. Clain-Stefanelli was made its first executive director. The collection is housed in the National Museum of American History.

Over the years, colleagues said, the Clain-Stefanellis were an inseparable force in coinage. They pursued donations from private collections and increased the Smithsonian's currency holdings from 60,000 items in the late 1950s to nearly 1 million last year.

The Numismatist magazine, in a 1996 profile, called her "a remarkable treasure in the world of numismatics."

Coin dealer Harvey Stack, of Stack's Rare Coins in New York, said the Clain-Stefanellis made the Smithsonian's coin collection comparable to world-class collections such as those of the British Museum and the American Numismatic Society.

One of the most important of their deals occurred in 1968, when the Clain-Stefanellis obtained for the Smithsonian one of the largest collections of domestic, foreign and ancient gold coins ever assembled. The 6,125 coins, then valued at $5.5 million, belonged to Josiah K. Lilly Jr., a pharmaceutical magnate.

Mrs. Clain-Stefanelli, once a historian of 19th-century Italy, said she saw coins as a palpable way to explore earlier cultures. For example, Greek coinage might explain how Athenians struck gold coins only during an emergency, such as the need to rebuild a fleet during the Peloponnesian War.

In the 1990s, Mrs. Clain-Stefanelli was a member of the Citizens Commemorative Coin Advisory Committee, which helps Congress approve coin designs and choose the historical worthiness of a potential commemoration.

She also helped persuade Congress to approve commemorative coins to honor the Smithsonian Institution's 150th birthday in 1996. She had served on committees to commemorate presidential inaugurations and on one for the U.S. bicentennial.

She was a recipient of the Smithsonian's Gold Medal for Exceptional Service.

Elvira Eliza Olinescu was born in Bucharest, Romania, and received a master's degree in history from what was the University of Cernauti in Romania.

She married Vladimir Clain-Stefanelli in 1939. They were in Germany doing research on coins when the Gestapo arrested them in 1942. Vladimir was sent to the Buchenwald concentration camp, and Mrs. Clain-Stefanelli, then pregnant, was originally put in a hospital. She later asked the Gestapo to let her join her husband at Buchenwald, where there was a contingent of Romanian refugees.

After the war, Vladimir took a cataloguing job at a Rome numismatic firm, and Mrs. Clain-Stefanelli volunteered her time at the same business.

They immigrated to the United States in 1951. She did cataloguing work in New York before coming to the Washington area in the mid-1950s. She became a U.S. citizen in 1956.

Among her publications was an 1,848-page reference guide, "Numismatic Bibliography."

Survivors include a son, Alexander Clain-Stefanelli of Arlington, and two granddaughters.