The early versions of ProScan, particularly those running in DOS, used a hardware-based anti-piracy and calibration system. The was a physical plastic card, similar in size to a credit card, that featured specific color patterns printed on it.
While you cannot print the card, you can download the official User Manual
Around 2002, a cracked version of ProScan 3.0 (or 4.0) was released that bypassed the Color Card check entirely. Search for "JBL ProScan cracked" or "ProScan keygen." These versions ask you to hit "Enter" instead of placing the card. Caveat: These cracks often have bugs in the graphic equalizer display.