Given the context of these disks, they would have probably been created on a genuine IBM PC or PC XT, which means a Tandon TM 100-2A.
Since I happened to have a PC clone with a pair of Tandon TM 100-2A drives in it, I tried them in there and read the disk with ImageDisk. It looks like it read it OK.
Funny thing is some of my old notes from back in the day say I tested a Tandon (TM 100-2A, DSDD 48TPI I believe) and it maxed out at 42 tracks. Of course, different revisions may differ.
Any rate, just commenting on this in case anyone else runs in to this. I recall there were some threads that discussed "maximum track preservation" of some different drives, but I don't recall any going that high.
Of course, going that far to the disk center was just begging for data errors.