The Shadow was sold my Megasoft in 1985-86. This was a hardware/software combination. Claiming a 99.9% effectiveness.There was also a GT Package that you would install in your 1541 to display the Track and Sector, very much like an Indus GT disk drive. Also added a reset switch and a device number change. I am not sure how you installed this.
From old Usenet postings it seems that there was questions on if this hardware actually worked or not. Megasoft was rumored to spend $400,000 on advertising for this produce. Also rumored that Megasoft went out of business because of this? Can anyone confirm or deny these rumors?