Rare David Clark 18399G-01 Aviation Prototype Headset 12948G-07 in box. I contacted David Clark customer service and they told me “The H8730 headset was a telephone communication headset that’s been obsolete now for at least 20 years.”
This is clearly marked prototype on both the headset and the box. I have no idea how it might differ from the commercially available model but I can’t imagine there’s too many of these out there for sale.