A lock-key system includes a key that can be inserted into a keyway of a lock cylinder, wherein said key is traceable by core pins or by locking elements which are movable in the cylinder core, wherein if there is a match, the cylinder core can be rotated by means of the inserted key. Lettering in the form of an impression and/or an embossment, serving as an identifier and including letters and/or numbers and/or symbols, is introduced into at least one lateral surface of the key shank—if a lateral profiling is present, into said lateral profiling. The lettering or individual letters, numbers, or the symbol or sub-areas thereof are traceable by core pins or locking elements having a correspondingly formed contact surface.