The wood box fits in the palm of a hand. The brass medallion inside it is the size of a sand dollar, or the bottom of a cup. It looks vaguely geological—like a fossil, sandy brown and eggshell white—and rests on a bed of velvet.
At first glance, “it’s almost like you’re opening a jewelry box,” says Anne Garner, curator at the New York Academy of Medicine Library. “Then here’s this bacteria.”
The medallion was made by Alexander Fleming, the Scottish microbiologist who first stumbled upon the mold that would become the basis of penicillin. Once he started fashioning little objects to commemorate his discovery, he couldn’t stop himself from churning them out.