"This cart will feature some of the best written tracks for the 2a03 sound chip ever produced, curated from over 2,000 .NSF files. This will be a limited collector cartridge numbered 00-99 on both the label and your screen."
It's part of Kickstarter Campaign for Battle of the Bits!!! More details @ https://www.kickstarter.com/projects/52 ... f-the-bits