frame number

Machine-translated from the German article

The frame number is a code specific to bicycle frames, consisting of a combination of letters and/or numbers, which the bicycle manufacturer stamps in or attaches to the bicycle by means of a label that is then painted over. It is the most important criterion for assigning a bicycle to its owner and is considered the most important basis in cases of theft for verifying ownership. Frame numbers are in most cases stamped into the bottom bracket shell.