"Other than returning the four parts for a refund (which we did) and documenting this behavior here, our only other recourse was to guarantee that these four specific parts were never sold as new again:"
Alas, one can completely remove Sharpie writing from metal with 99% isopropyl alcohol. Did they make a better choice? This looks like Sharpie writing to me.
You can also remove sharpie writing using sharpies and a wet wipe - write over and wipe while its still wet. The dry pigment will dissolve in the solvent in the fresh ink.
One spray of brake cleaner and it's gone. Cheaper to use a carbide scribe or simply get a shard of glass or ceramic and physically scribe into the drive. Now they're permanently used drives, no debate is possible.
Alas, one can completely remove Sharpie writing from metal with 99% isopropyl alcohol. Did they make a better choice? This looks like Sharpie writing to me.