[beagle3]

IIRC, Quaid software's Copywrite on the PC was able to reliably duplicate weak bits, and had a companion called "zerodisk" which would -- in cooperation with marks left by Copywrite -- emulate laser holes.

I remember at least one copy protection system I analyzed, which get "free reign" into writing tracks, by configuring the drive to write just one huge sector per track (which ended up being longer than the track), end encoding the sector gaps "in band" which later became "out of band" because the main track header was overwritten (and an "in band" one became out-of-band).

It was interesting, but I have no nostalgia for that.