The chart is a bit hard to read and we'll look to see if we have a better copy in the link-vault.
@Will Penfold If 60 years following Columbus you started selling silver because of the discovery of the New World you would seem mad. But in the next 60 years silver collapsed.
What it purports to show is the effect on silver's valuation of the Spanish discovery and appropriation of the New world mines of Potosi and Mexico's Zacatecas. The timeframe is roughly 1300 to 2000:
Via InvestorsHub, 2006.
$14.94 up 19 cents last.
The numbers seem about right although I don't have the original database.
As the technical analysts would say: "Approaching long-term oversold".