If I was Leonardo or a double digit millionaire I'd buy this poster in a minute. Of course I would throw down a $725K offer first. I guarantee this sucker will double in value over the next 30 years. The problem is that the annual rate for ROI, which is pretty good right now, is only 3.6% if it doubles in 20 years and only 2.4% rate if it doubles in 30 years.
So essentially one could buy a McDonald's franchise and double their money in ten years for the same price of the poster and get a better return... It will have to go to an investor/collector...