Not so difficult. In Germany the first 1-3 letter(s) are designated to the town of registration D - Düsseldorf, S - Stuttgart, B - Berlin etc. and then 1 or 2 digits are letters (FU in this case) and then 2, 3 or 4 numbers (107 in this case). So in Germany you have limited 'free choice' of numberplate.Pretty cool he was able to incorporate 107 into the plate.