Please check your coin again. The Denver Mint didn't open until 1906. If the mint mark is actually an "O" your coin was minted in New Orleans; there's more information at the Related Question.
a dollar
value of 1845 us five dollar coin
It's a common dollar coin that's face value
There was no fifty dollar US gold coin produced in 1940.
One dollar.
Check that coin again. The U.S. has never minted a two dollar coin.
$1.00
Approximately One dollar
Check that coin again. There was no such thing as a US dollar (or the United States) in 1756.
A pewter coin is also known as a Continental dollar. Depending on the condition of the coin, the value of an original pewter dollar could be as little as 1,000 US dollars to 15,000 US dollars.
Look at the back of the coin for "HALF DOLLAR" no US dollar coins were struck after 1935.
72.90