Also, some early 1600's cobs had platinum mixed in because the Spanish thought it was a worthless metal and an easy way to cheat people.
The Vellon cobs interest me most and actually very little is known about them today. I have found Vellons Maravedis cobs and had collectors argue that they are not silver but 100% copper. Yet the cobs are obviously silver. Why the Spanish even made these is a really odd thing to say the least. Some say they were trying to boost the value and acceptance of the copper Maravedis, others say they were a cross between the reale and copper cob, and still others just flat out refuse to admit they even exist. Go figure?
But I have collected about 50 of them so I know they exist. They are out there but very difficult to find.
I personally suspect that some Vellons cobs from the 1600's may be a mixture of copper and platinum (not silver).
Badger