Like so many notes, and not unduly so, it is an Albrecht Durer painting from the 16th century, there were actually a series of notes issued through the 1926 5 RM note that had Durer subjects on them. Curiously even for the inflation notes of 1923 they were attractive designs and quite pricey. The 1926 5 RM note is difficult to find in Uncirculated, even though they circulated through 1945 along with the 1942 nazi note.
Durer subjects appeared on many German notes, on up to the 1980 series, with his "Venetian Woman" on the 5DM note, this is a 1960:
(http://www.geocities.com/scottishmoney/banknotes/germany/germany51960dtl.jpg)
(http://www.geocities.com/scottishmoney/banknotes/germany/germany51960.jpg)
One of my personal favourite German notes. Even if she is a lovely Italian ;D