I have contemplated and sketched out what would be required to build a slot loading sd card reader. Ultimately, I believe a vertical mount door loading mechanism* is cheaper, more reliable, and certainly has a decent aesthetic.
Sony did release drives, DGR looks at one in this video for example https://www.youtube.com/watch?v=CzwtCBj5jEs . It's yet another example in the weird graveyard of replacements for the 1.44MB floppy that didn't catch on.
Yes, it’s disappointing, but I chose to publish this anyway to counter publication bias, and to maybe motivate someone else to come up with a different method to analyze what’s on these dummy MiniDiscs!
Dummy boxes for retail stores that keep the real discs behind the counter wouldn't need any disc at all.
Dangerous is probably a really early MiniDisc as it was a recent album at launch in 1992. Perhaps it was created for launch promotions, trade shows etc. where they needed to show physical MiniDiscs and packaging but hadn't actually mastered and manufactured the real deal yet in quantity?
IPR licences are complicated and maybe Sony did not have contracted rights to the music on MD format but had committed $$$ to the campaign? Maybe Jackson had good lawyers when he sold them the catalogue!!
Are MD pressed or recorded? It might be interesting to see if two Michael Jackson promo discs are identical.
Pre-mastered MDs are pressed and the format is physically similar to CDs. I would be interesting to put this disc under an optical microscope, I assume it would look similar to a regular pre-mastered disc but perhaps it's actually a recordable MD (which look very different) or some kind of R&D experiment.
I took a bunch of optical images of MDs and other formats here for reference:
MiniDisc is truly how the future of audio would have looked like in a parallel universe.