Every time this happens I'm curious how it ended up there. Someone just bringing a box of junk to goodwill and actually not caring, or is someone having an "oh shit" moment when they read this because they didn't actually check the box that thoroughly? The sadder story, and the older the tech the more likely, is that the person who owned it isn't with us anymore, and this is just someone cleaning up their house.
For reasons, I abandoned a storage unit containing (among other things) numerous prototype and unreleased hardware devices, the storage company will just have auctioned the contents. Sooner or later one will appear on here I'm sure
A lot of these prototypes aren't that closely guarded. As a run-of-the-mill employee at Google I ended up with a bunch of random pre-production Androids and IOT devices from the dogfood program. You were supposed to give them back most people I know didn't bother -- Google isn't a very threatening employer -- and I think I even accidentally gave some of them away with other old electronics when I moved.
There was also a room full of to-be-recycled electronics in 42. It was open to employees so they could recycle personal stuff but it was absolutely full of (I assume non-confidential) prototypes including stuff that looked like it was from Google X. I was too scared to take any of this stuff but was really tempted to grab the carbon fiber gliders and weird nest devices.
Maybe they know it's a prototype and purposefully "accidentally sell it" just to see who ends up buying it. Especially if it's a prototype for an old tech product, the company that made it either doesn't exist anymore, or the device is so old they just don't care.
If I had to guess that Xbox was a take home unit for testing Xbox Live. The production date was about a year after retail release, and a home unit for testing an early version of live is the kind of thing that could end up in an ex's garage and goodwilled.
