To the patron who said that they would give me half a million dollars --- I won't forget.
I had a patron come up to the info desk with a color photograph of a painting that his old landlady gave him over 40 years ago. This was an elder patron and he admitted that he wanted to "get his ducks in a row" while he could still "get around."
He had no idea who the painter was, but he was hoping that we, The Library, had the right resources. The best I could do was find a couple of online resources that might have been the right artist or not, depending on how you interpreted the signature. He seemed pleased with what I had found and said that he was going to visit one of his friends who works at an art museum. Seems like the first place I would have gone, but it was nice he thought of the library. He said, "Who knows? Maybe it's worth a million dollars, I'll give you half of it!"
With a couple hundred grand on the line and a couple of hours after he left, I continued to do some more research into that particular artist and found a website that listed their recently ended auctions. The highest auction ended at $15,000. So Generous-Patron, your estimate of $500,000 was pretty far off, but I would more than gladly take a couple grand, you know where to drop off the check.