This wouldn't be the first ThinkPad with a transparent display. The ThinkPad 755CV/CDV[0] let you lay the screen on a light projector to become an LCD projector.
Wow the overhead projector. Such a blast from the past. This is when things got even more boring than the death by powerpoint of today :) usually black and white and a nerdy professor speaking in monotone for a whole hour or more.
I wouldn’t count that as a transparent “display” since it needs a light source when detached, or it wouldn’t be of much use.
So if we only consider self-contained transparent displays, this is indeed a first?
Wow I’d forgotten all about this. There was so much hype about this when it came out.