Take, for example, the $4 gold piece, minted in 1879 and 1880.
Also known as a Stella, the $4 coin was produced to explore the possibility of the US joining the Latin Monetary Union.
It was meant to contain a quantity of gold similar to that of the standard LMU gold piece, the 20-franc Napoleon minted in France, Switzerland, and other countries that belonged to the Latin Monetary Union.
The Stella was a pattern coin, which means it was proposed and produced in small numbers but never received approval for public circulation.
Even though just a few dozen Stellas are known to exist, four will go up for sale on Sept. 23 in Los Angeles when auction house Bonhams puts the spectacular Tacasyl Collection – 27 American gold coins in all – on the block.
The 1880 Coiled Hair Stella, featuring the image of Liberty with a braided plait on top of her head, could fetch $1.5 million or more.