Please look at the date and denomination again. The U.S. did not issue any half dollar coins dated 1804.
The US didn't strike any half dollars in 1804.
The U.S. didn't make any half dollars dated 1804.
1866 was the first year for shield nickel's, the only US coins dated 1804 are a Half Cent,Large Cent,Quarter,Dime and a Dollar.
is it the biggest
A dollar
Kennedy half dollars are 30.6mm in diameter and 2.15mm thick.
About the size of a US half dollar.
In your search box type in [1804 dollar] an click on images. This will bring up pictures of the coins.
The average cranberry can get to the size of a quarter or half dollar.
The Diameter is 30.6mm, thickness is 2.18mm at he rim.
The site under Related Links below has a number of very good images.
It's the same size as all other U.S. half dollars.