A collector of rare books ran into an old friend who told him he had just thrown away an old Bible that he found in a dusty, old box.
He happened to mention that Guten-somebody-or-other had printed it.
"Not Gutenberg?" gasped the collector.
"Yes, that was it!"
"Do you know what you have done? You've thrown away one of the first books ever printed. A copy recently sold at auction for half a million dollars!"
"Oh, I don't think this book would have been worth anywhere close to that," replied his friend. "It was scribbled all over in the margins by some guy named Martin Luther."