“FE-Schrift or f?lschungserschwerende Schrift (falsification-hindering script) has been the only typeface used on new vehicle registration plates in Germany since November, 2000. It was designed for the German government in the late 1970s in the light of Red Army Fraction terrorist activities, when it was discovered that with the then standard font for vehicle registration plates (DIN 1451 road-sign font) it was particularly easy to modify letters by applying a small amount of black paint or black insulating tape. For example, it was easy to change a “P” to an “R” or a “B”, or an “L” or “F” to an “E”. Modifications to FE-font plates are somewhat more difficult as they also require the use of white paint, which is easily distinguished at a distance from the peculiar retroreflective white background of the plate, in particular at night.”

From:
http://en.wikipedia.org/wiki/FE-Schrift