How can you tell if a painting is a modern forgery? Mid-20th-century nuclear bomb tests may hold a clue.

For years, scientists have been refining techniques to determine the age of a painting using radiocarbon dating and the lingering effects of the tests. Now, a team of researchers has dated one such artwork using a paint chip the size of a poppy seed, according to a study published on Monday in The Proceedings of the National Academy of Sciences.

“It’s an amazing technical achievement,” said Greg Hodgins, a professor at the University of Arizona who oversees a lab dedicated to radiocarbon dating and was not involved in the study.

The ‘bomb peak’

Developed in the 1940s, radiocarbon dating allows scientists to determine the age of a wide range of materials — including fossils, cave paintings, parchment and even human remains — by examining the types of carbon atoms they contain.