And, now, those notes sell for over $100 each in uncirculated condition, simply because it's denominated in "dollars" and has the largest numerical denomination history. Had you bought one in 2001, when they were worth $5 apiece, that would have yielded you a CAGR of around 40%. Sometimes, I kind of want to kick myself for missing out on that train. :)

More as a collectable than anything else.

You should look up "worthless." Even kindling counts as value. Try burning Bitcoin.