IBM 5170 - Fixed Disk/Diskette Drive Adapter Test Diskette
I bought this floppy via eBay.
It appears to be a more thorough version of the controller test contained on the IBM 5170 (AT) diagnostic floppy.
It is possible that this is the diagnostic program referred to on page 120 (PDF page 6) of the magazine article at here.
Quote: "When the problem first became apparent, he says, IBM sent dealers a controller-card diagnostic program with instructions ..."