The Guinea and its fractional denominations were withdrawn from circulation in 1816 and effectively replaced by the Sovereign and Half-Sovereign (One Pound and Ten Shillings respectively).
When the Guinea was in circulation, it was worth One Pound and One Shilling (or 21 Shillings).
The Shilling was progressively withdrawn from circulation after decimalisation. The Shilling became 5 New Pence in the new decimal currency.
A Half-Guinea in modern terms, would be the equivalent of 55 Pence.
The British gold Half-Guinea was last minted in 1813. It was effectively replaced by the gold Half-Sovereign in 1817.
All denominations of the Guinea coin were made from gold, they were never made from copper.
1963 COPPER penny is worth half a billion dollars.
All copper-nickel half-dollars (1971-present) in circulated condition are only worth their face value.
I've seen them for sale at £250
the old copper cooler is worth 250
The guinea coin was not made after 1816.
If it's dated 1965-1970, it's 40% silver and currently worth about $5. 1971 or later is copper and nickel, worth 50 cents.
It very much depends on which 1799 coin you have, and also on its condition. If copper, then you could have a farthing or a halfpenny. No silver coins have that date, but gold coins of 1799 include the third guinea and guinea. See the related link for more detailed information.
All circulation half dollars dated 1971 and later are made of copper-nickel and are only worth 50 cents. An uncirculated one in its original package might be worth 80-90 cents.
How much is a UK half pence worth
1 penny
U.S. half dollars aren't solid silver. They're 90% silver with 10% copper, currently worth about $10.
How much is a UK half pence worth