The German physician Philipp Franz von Siebold spent six years stationed in Japan in the 1820s, and is largely credited with introducing Japan to Western medicine.

Siebold was also a botanist and art enthusiast, and part of his collection eventually ended up in the National Museum of Ethnology in the Netherlands. However, the artist behind six paintings, created in Western styles, remained unknown—until a group of researchers took a closer look at records kept by Siebold’s descendants.

The six paintings were created in watercolor, and in Western styles, leading curators to believe they were done by an unknown Western artist. However, a group of researchers, led by a prominent expert on famed ukiyo-e artist Hokusai, examined the paintings recently and decided to investigate further.