Hat tip to Shappie on the Marathon Discord for spotting this. Yours for only $893!
Wondering what this has to do with Marathon? Have a look in the Blasts from the Past section. As far as I've been able to find, VictorMaxx never did get around to making the retail headset Macintosh compatible. It was expensive, sold poorly and was quickly eclipsed by competitors. Bungie gave up on VR by the time Marathon 2 was in development.
Of course, to really complete the Marathon VR accessory set you would also need the ADB Automatic Assault Rifle with Grenade Option... if you could find one. The unit Bungie demoed at Boston Macworld in August 1994 and displayed at their office in later years was built out of an off the shelf toy: a Larami Z-Matic M16 cap gun. I'd be surprised if more than a few (or even one) ever existed.
I had a hard time finding photos of an unmodified Z-Matic M16, but I've linked a copy of an eBay listing for a less fancy variant below. Despite the name, it seems to be modeled after an AR-10 rifle from the late 1950s.