That was funny!
In the humorous posters defense, it was a pretty weak starter. Where did the information come from that he had collections in museums? What's the reason there's no paper trail?
Reminds me of the posts, "I have this old S&W, can you tell me when it was made, the name of the guy at the factory who shipped it, and what it's worth?" - and that's it!
If you want information, need to let us know what you already know. How about the father-in-laws' name? If he's a famous collector, a rich guy like rburg might know of him.