The invention provides for a label such as a temper evident holographic or diffractive security label that consists of at least two separate microstructures (30, 31), one exhibiting a holographic or diffractive security image, the other a non visible non-diffractive structure which controls differential release of a reflector or semi reflector layer (27) to display a separate visual message upon removal of the label by tamper. The advantage over previous prior art devices is that both the diffractive message and the tamper evident message are encoded within the microstructure without any need for additional coating or print layers in the device.