The framed oil paintings were found by a 64-year-old man at a highway service station in the Bavaria region last month. The man later handed the paintings to police in the western city of Cologne, the police department said.
Officers have launched an appeal for the owner of the paintings. An initial assessment from an art expert concluded the paintings were likely original works, police said.
One of the paintings is a smiling self-portrait of Italian artist Pietro Bellotti, dating back to 1665.
The other painting is of a grinning boy in a red cap, date unknown, by the Dutch artist Samuel van Hoogstraten.
In the later part of the 17th century, the elite of Hague “lined up to sit” for Hoogstraten’s portraits, said the Collection.
The artist also wrote an “Introduction to the High School of the Art of Painting,” which was published the year he died, in 1678.