Boy, I've got to check this forum more often as all the good Jaguar talk has left my beloved JI.
Has this item been on eBay yet? Hmmmm. I highly doubt Atari would have had a headset for the JVM completed before the JVM. You think of what has to happen for such a simple item to being "officialized" such as design, patenting, etc, etc. You have got to think all it is is one out of a box-o-headsets Atari used for testing and development purposes.
Back in 1999, which were the glory days of Jaguar Proto collecting, I had just gotten my modems and went into my neighborhood Radio Shack, not just to get a case to mount them in, but also compatible headsets. The stars must have been aligned perfectly that day as they had two $50 headsets with voice activation, PTT, volume control and seperate mic/phones plugs clearanced for something like $9 each! These are like the porsche of headsets. I would have bought more for others but they were the last two in stock. Very sad...
Anyhoo, please keep the forum updated as to what they ended up being, be it the seller or a inner-community buyer.