Doesn't sound like a SCSI card part number, especially from NatInt. They made Digital I/O cards and the like for the Mac. If it's an IDC50M header connector like a MoBo or internal SCSI device that's sticking out the backplane, it's definitely not a SCSI card.

NatInt used that connector, but it's for hooking up all sort of lab equipment/sampling and digitizing analog inputs etc.

edit:

Bingo!

http://www.ni.com/pdf/manuals/320640.pdf

http://www.datasheetarchive.com/NB-MIO-16X/Datasheets-UD1/DSAUD003430.html

Sounds like a typo or simple mistake substituting an "M" for the "N" for the NuBus designator, but "MIO" would be NatInt's Model Number terminology for a Multifunction I/O Card.