The 2nd largest DBEM format, 12 in (300 mm) disks were used almost exclusively in industrial, government, medical, and enterprise archiving, where huge volumes of records needed to be stored permanently. They were most often ablative WORM, with capacities typically under a few dozen gigabytes. Drives were large and expensive, and media was usually handled through high-capacity disk changers. Few of these systems remain, and documentation is especially scarce.

There is very little information about this format other than what was included in the original Mercari listing where I found the disk¹⁾. There are no references to this specific model of or series of disks. The aforementioned listing associates the disk with the Fujitsu M-Series of computers, but this has not been verified.

The dimensions of the disk are 338 mm wide × 349 mm tall × 21.3 mm thick. The cartridge has a beige / tan casing and orange write protection tabs. The inner disc appears to use CAV sector placement, but whether it is Magneto-Optical or not cannot be determined at this time.