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