This post - the title made me remember ... ( as a credit card is about the same size as a business card )

A Linux Business Card CD is a miniature, credit-card-sized optical disc containing a stripped-down, bootable Linux operating system. They hold around 50MB to 100MB of data and were highly popular in the early-to-mid 2000s

More info at https://en.wikipedia.org/wiki/Bootable_business_card