The invention relates to a lock-key system, including a key that is insertable into a key channel of a lock cylinder, and traceable by core pins or by locking elements that are displaceable in the cylinder core, wherein in case of 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 and in case of a lateral profiling, into the 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.