This is the self-booting (via PC-DOS) Reference/Setup disk needed to configure the Tandy 5000 MCs NVRAM with MicroChannel card descriptions so the machine will boot. Prior to the Radio Shack corporate auction on July 10, 2017, this disk was unobtanium. During the auction, I purchase the corporate museum’s 5000 MC and the machine had the 1.02.03 reference disk sitting in the floppy drive! Please pay appreciation forward and help keep these very unique machines alive and running forever! The 5000 MC Reference Disk has a label that indicates the RS Catalog # is 25-6000.