Philippine Banknotes: 2008 100 Peso UP Centennial Overprint
An overprint is an additional mark or print on a banknote. These prints commemorate a certain event and are the counterparts of commemorative coins. Instead of having a new design, the banknotes with overprints are your ordinary everyday banknote with just a additional print. An example is the 2008 100 peso University of the Philippines Centennial overprint.
I’m not sure how many of these were printed, but I find these in circulation up to this day. Its an ordinary 100 peso bill. The only feature that made this different is the UP logo indicating that 2008 is the 100th year of the university.