Potosi was a miserable place, high in altitude, causing headaches and nosebleeds. Miners took to chewing coca leaves (baked hard) just to ease the pain. But the silver -- glistening silver -- made it all worthwhile despite the altitude of 13,780 feet (plus another 1,900 feet on the slopes).
The beautifully mottled sepia tones, with splotches of dark chocolate and hints of mint, give this piece authority. The colors look like the mountain. But more to the point, these salty deposits belies a tale of malfeasance at the mint.
The evidence is clear: the cob is debased (less than the required 93% fineness) and just shy of its required weight of 27+ grams. Produced under the darting eyes of the on-site assayer, Pedro Trevino, it was a deliberate silver grab.
Pedro worked at the mint from the late 1630s until about 1645 or 47. The cobs produced during his watch were marked with his monogram: an R with the crossbar of a T placed across the top. This TR is seen on the left side of the Hapsburg shield underneath the P that stands for Peru (or Potosi). Since the crossbar of the T extends both left and right, the cob is though by experts to be a later style from the 1640s.
In a subsequent investigation by royal officials sent by the Phillip IV in 1648, it was decided to deport poor Pedro back to Spain where he met his end, dangling, at the end of a rope. Other corrupt mint officials were punished as well, and the whole coinage of Potosi was redesigned in 1652.
And so, we have this beautiful cob as a testament to these events of three centuries ago. You just have to love the primitive nature of this piece -- haphazardly struck on an odd-shaped flan. And the corrosion -- oh sweet corrosion -- is the punch-line.