One day in spring 1979, Robert E. Heggestad walked into a small antique shop in Arlington, Va. Mr. Heggestad, a young lawyer from Iowa, was looking for Chinese carpets. The selection of rugs in the small back room was disappointing, and he was about to leave when he noticed a handsome rosewood cabinet behind the cash register.

The owner wanted a sum that far exceeded Mr. Heggestad’s budget  a colossal $600. “I was just out of law school, I had no money and no business buying it,” he said. But the owner was willing to take installments of $100 a month, and into Mr. Heggestad’s possession fell an incomparable scientific treasure.

The cabinet belonged to Alfred Russel Wallace, the English naturalist who conceived the idea of evolution through natural selection independently of Charles Darwin. It arrived earlier this month at the American Museum of Natural History on loan from Mr. Heggestad and will be on display starting Tuesday, the 150th anniversary of the publication of Darwin’s “On the Origin of Species.”

Image A drawer from the cabinet exhibiting a collection of butterflies. Credit... Robert E. Heggestad

The cabinet is “a national treasure,” said David Grimaldi, a curator at the museum, citing its historical value and Wallace’s role in the theory of evolution.