IX. Never swap bullion coins for U.S. $20 gold pieces.
I'm curious as to why? Is it just the premium?
A gold Brittania has a face value 50 times that of a silver Brittania. What happens when industry is screaming for delivery of silver and there is a real shortage?
With gold having a high specific gravity it can't be adulterated in such a way that it will pass a SG test unless the price of platinum goes lower than gold, most unlikely. I can see a situation where silver is needed more and more but if the price exceeds that of gold, then gold can be used as a filler by cheats. Again, unlikely that silver price exceeds gold because of their relative SGs.
How close can the gold/silver price ratio get?