Old French coins would be called Francs. now the currency of money there is called Eros, but very old French coins were called Francs. Singular is Franc. Plural is Francs.
A drachma.
A franc
frank
An old 6d coin (half a shilling) was called a tanner
The old French coin starting with the letter "E" is called the Écu. It was a silver coin used in France from the 13th to the 18th century.
Livre
The 5 Franc coins from the 1800s are called 5 Francs.
A coin collection is called, well, a coin collection. The hobby of collecting coins is called numismatics.
In French, 'huguenot' was the name for protestants. There is no old French coin known as a 'huguenot' - but there is a 1924 US half-dollar called 'Hugenot-Walloon tercentenary'. (follow link)
There's no US coin called an "old buck coin". What you have is a modern Presidential dollar worth face value only. The dates 1857-1861 are the years that James Buchanan served in office. The minting date 2010 is on the coin's edge.
Referring to coin flipping, heads and tails are not plurals. They are old genitives, and could be written head's and tail's.
A Kandahar, Afghanistan coin is called an Afgani.