I would think that will be tough, maybe some sort of professional appraisal, if there is such a thing for vintage audio equipment. Just because you tell the insurance company my very unique, one of a kind H2 are worth $2k doesn't mean they will pay that if there is a loss. I have been thru a flood and insurance companies search out most item values by comparables in the marketplace. At the very least i'd take detailed pics or video and store them somewhere safe. Not a bad idea to do with all the contents in your home. Like in a safety deposit box at the bank, or exchange with a family member for safe keeping. Put it on a usb thumb drive.
When my home was flooded in 2012, the insurance company gave me an Excel spreadsheet to document my house contents and values. I had taken plenty pics of inside beforehand. Without detailed pics or video, it is super tough to account for everything in your home of value. I did mine room by room with the pics I took, and my memory too.