The was originally pressed as a physical CD-ROM or laserdisc (depending on the SKU) designed for one purpose: to calibrate Sony’s professional and consumer CRT (Cathode Ray Tube) displays, particularly the legendary PVM (Professional Video Monitor) and BVM (Broadcast Video Monitor) series.
Specifically mentioned in older, high-end Sony service manuals for calibrating pickup assemblies. Sony Test Disc Yeds-7.rar
Others told darker tales. They spoke of a "Track 99" on the original disc—a track not included in the The was originally pressed as a physical CD-ROM