A data storage cartridge for a data storage disk drive has a latent illuminance marker. A reflective surface on the cartridge increases the intensity of the irradiance on the marker and illuminance from the marker. A light source illuminates the marker and the marker emits phosphorescence. A photosensor detects the emitted illuminance, and the decay time is determined. The decay time is checked to provide identification of different types or generations of data storage cartridges or provides a secure keying mechanism for authorized access to proprietary software.