The mechanical movement includes a checking device which is a passive indicator element. The passive element is fixed to a fixed support portion of the mechanical movement. The passive element may be a strip or a plate fixed to the fixed support portion of a regulating member and configured to vibrate according to one or more clearly defined vibration frequency components following the vibration of the mechanical movement. The vibration frequency components of the strip or plate define an acoustic signature specific to the timepiece to allow the authenticity of the timepiece to be determined by a measurement of the acoustic signature using an acoustic measuring system.