This simple little program tests for two problems some first run 1581 drives might have.  As stated in a newsgroup post I found:

The first one involved an improperly grounded jumper (J1) on the PC board
inside the 1581 disk drive.  Allows the drive to use the 6 ms step rate.

The second involved a bad batch of WD1770 chips that were later replaced
with the WD1772 chip.  A typical symptom of this problem is a corrupted
directory after a disk copy.