The only thing is that they were all fake. My friend's hobby wasn't collecting memorabilia, it was making fakes. He was quite open about the fact that none of it was real and would happily describe how he created each piece.
Edit now that I’ve read the article: I appreciate that it appears that the museum wasn’t dismissive of the claims and verified the forgery with their own analysis. But the original article was posted on the museum’s website, so who knows.
One of my favorite examples is Gibson replica guitars with period-accurate serial numbers, but the serials are intentionally stamped during the wrong step in the painting & finishing process to signal that they weren't assembled at a Gibson factory.
His heirs probably won't be so forthcoming.
I remember he did a pretty cool recreation of the gun from Blade Runner at least.
Of course, Etsy is probably the main platform to sell these, and it's full of copycats so anything that looks like it could make money will quickly have cheaper made duplicates flood the market. And not just Etsy, inventions like the fidget clicker box and -spinner saw the might of Chinese manufacturing and drop shipping spin up almost overnight and flood the market with them.