A modern Gold Eagle bullion coin is 1/10th of an ounce, the older Liberty Head series coins weigh 8.359 grams.... so a $5 gold coin does not weigh an ounce to start with.
The U.S. has struck $1 coins since the 1790s (with some interruptions) and at about a half-dozen mints, so you need to be MUCH more specific. The only general answer is that $1 coins dated 1971 and...