The second-to-last banknote design series, designed by Tapio Wirkkala, was introduced in 1955 and revised in the reform of 1963. It was the first series to depict actual specific persons. These included Juho Kusti Paasikivi on the 10 markkaa, K. J. Ståhlberg on the 50 markkaa, J. V. Snellman on the 100 markkaa and Urho Kekkonen on the 500 markkaa (introduced later). Unlike Erik Bruun's series, this series did not depict any other real-life subjects, but only abstract ornaments in addition to the depictions of people. A popular joke at the time was to cover Paasikivi's face except for his ear and back of the head on the 10-markka note, ending up with something resembling a mouse, said to be the only animal illustration in the entire series.