It is an InterMedia floppy disk controller board for the Mac. This version was called InterMac and developed largely by request of Linotype. They wished to sell their software based on the Mac, but with the ability to read older style floppy disks of both 5.25" and 3.5". The controller board would read the Apple DOS 3.2 and DOS 3.3 5.25" GCR disks. Similar boards were developed for PC, PS/2 and early on (pre 1987) S100 Bus.
It has nothing to do with SCSI
The connector at the back is 50 way and went to a flat 50 way ribbon cable. The cable was based on the 50 way 8" disk interface, but with changes to that it could be used with drives of any size, within an InterMedia case. Thus could include 8", 3" and even the Apple super drive to handle the 800KB variable speed 3.5" GCR disks reliably. However, the controller board could read many Apple 3.5" GCR disks reasonably reliably, but with at times raised error rate.
The software was written with a CommonView library so code was 99% in common with the main Windows version. Care was taken within the code as the Motorola and Intel use different Endian for storing numbers. The final code was made fully compatible with both platforms