It would be fascinating to find out where some of these parts come from. CuriousMarc had a video sometime ago where he got a batch of exotic HP custom ICs for h

It would be fascinating to find out where some of these parts come from. CuriousMarc had a video sometime ago where he got a batch of exotic HP custom ICs for his HP 9825 from a random seller in China. He first thought they were counterfeit, but after testing and decapping they turned out to be genuine. I don't think there's any profit in cloning such rare, old chips. Even in China I suspect fab runs are too expensive to justify making old chips for a handful of retro-computing enthusiasts. I think it's more likely these are parts pulled from old boards before recycling or forgotten new-old-stock someone found in a corner of a warehouse somewhere.