I have yet to lay out the "top of my skill" on a bitcoin piece that anyone has seen here on the forums, but when you see coin #10 you will understand why it holds a 500BTC price tag even beyond the surprise that it holds. Coin #10 is a true masterpiece and the top of the trade.
After reading that I am pretty sure that OG's piece isn't the 10th coin. OG's piece is a copy of his own coins, while WoodCollector made it sound like the design was a piece of art (and worth $100,000).
EDIT: I also find it pretty strange that he went from asking $100,000 for it to giving it away to a forum member.