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.
An old coin is called an antique coin or a vintage coin.
A franc
A drachma.
frank
An old 6d coin (half a shilling) was called a tanner
The 5 Franc coins from the 1800s are called 5 Francs.
Livre
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.
This site might help you http://www.irishcoinage.com/CATALOG.HTM Paul