In 1989, a heart surgeon named Juan Suros VXII, from Coronado, California, who had been a member of the American Numismatic Society for over twenty years, was arrested and charged with grand larceny for stealing over $500,000’s worth of rare coins from the Society’s holdings. After a search of Suros’s room at the Harvard Club in New York City revealed that he had been smuggling out valuable coins, the Society sent Alan Stahl, a curator at the time, to San Diego, and entrusted him with the task of identifying the remaining stolen coins from Suros’s deposit box.

It took over a year, but, thanks to Stahl’s scrupulous eye, all the coins were returned. These months of Stahl’s life in part justify the extensive security measures that now guard Stahl’s current office in the Special Collections section of Princeton University’s Firestone Library, where he is now the Curator of Numismatics. A first-time visitor first locked all belongings in one of the lockers that line the entrance to the Rare Books Collection, signed in at the front desk, donned a security badge, and followed Stahl to the door of his office, which he unlocked with a combination of a key card and a retina scan, as if he was at the entrance of the headquarters of a secretive spy syndicate. The gadget recognized his eyes through the square frames of his black glasses. “It’s good when it works,” Stahl said after the tight click of the unlocking door, muffled in the bunker-like basement.

Like many basements, the room was packed with furniture and cluttered: faculty members’ desks covered in papers, shelves stocked with books, little free space. Unlike most basements, there was, of course, no mold or must, nor was there a metallic stench, as one might imagine when thinking about coins. Stahl, now almost 70, was dressed in a blue plaid shirt with a spotted interior collar, black suit pants and polished black tennis shoes that squeaked with each step. He sat in his swivel chair and began to fidget with a desk drawer.

“We can advertise ourselves as the oldest continuously curated coin collection in the Western hemisphere,” Stahl said with a proud smile, his palms facing upward in vague reference to Princeton itself. He recounted how, in the 1830s, the first few items of Princeton’s collection were donated by an alumnus. Stahl pointed to a framed board of coins hanging on the wall beside him. “These actually are casts, not coins—electrotype copies of ancient Greek and Roman coins from the British museum. Then we started getting real coins.”

Since the collection is funded in part by the university’s other coin collection, so to speak (it maintains a $22-billion endowment), it’s still growing rapidly. Just last December, Stahl closed an acquisition of a large number of Byzantine coins costing “in the mid-six figures.” According to Stahl, most experts consider the most valuable coin in Princeton’s collection to be the 1792 American “half disme,” the first coin issued by the U.S. mint, of which there are only a few hundred copies of varying condition (in 2004, one 1792 half disme was sold at auction for $138,000). “George Washington had promised to get the mint going, and Congress was getting very impatient,” Stahl explained, as if telling a well-known fairy tale. “In his State of the Union address, he wanted to be able to say the mint was operating. So—the story is—he took some of his and Martha’s silverware, and brought it over to have it minted into this small edition of silver coins.”

Unlike many curators and coin buffs, who often begin collecting as “anti-social teenage boys,” Stahl has never owned a private collection—not even when he was a boy himself, growing up in Philadelphia. He became interested in coins later, as an undergraduate at U.C. Berkeley, before he earned his PhD in 1977 from the University of Pennsylvania in Archeology and Art History (his dissertation was titled “The Merovingian Coinage of the Region of Metz”). He then served his two-decade tenure as a curator at the American Numismatic Society. When the society cut its six curators to one, Stahl moved around for a few teaching jobs before settling into his current position at Princeton in 2004. Eight years later, Stahl married William Hanauer, the former mayor of Ossining, N.Y., a town not far north of New York City known for Sing Sing maximum security prison. Stahl commutes to Princeton from Ossining, where he and Hanauer live in a renovated Presbyterian chapel.

Stahl shook his desktop’s mouse over its mousepad, a miniature replica of a Persian rug, and checked the analogue clock pictured in the screen’s bottom left corner. It was time for him to go next door to host an undergraduate art history lecture, as he does from time to time. To leave the room, Stahl again used his special key, a white magnetized card that hung from his lanyard. (No retina scan this time.) Next door to his office, where he waited for the class to arrive, a display of coins was set out on a table. “Coins are a form of evidence for history, art and archeology,” Stahl said as he walked across the table to a sleeve of recently acquired Byzantine coins, flipping each one over for closer examination. “Often what they tell us are things that are lacking in the written record or sometimes they give us a story that’s different from the written record.” Each time he picked up a coin, pinching its edges, he was careful to lay it back in its place, exactly as it had been before.