The following Q&A is excerpted from Clifford Mishler’s Coins: Questions & Answers
Q: I have seen early U.S. gold coins that appear to be bigger than gold coins of like denominations of later years. Did they at one time have more gold in them?
A: The gold coins of the 1790s and early 19th century were larger in diameter and thinner than gold coins of later years, although there was not a significantly higher amount of fine gold in these early coins. This was the case with most denominations of silver coins as well. The half eagles ($5 gold) of 1795 to 1829, for example, had a diameter of 25 millimeters and a fine gold weight of 8.02 grams, with the diameter being reduced to 23.8 millimeters from 1829 to 1834, then to 22.5 millimeters from 1834 through 1838, with the fine gold weight being 7.517 grams for 1834 to 1836 and 7.524 grams for 1837 to 1838, with the diameter being reduced to 21.6 millimeters and the weight adjusted to 7.523 grams (or .24187 ounce) commencing in 1839, which standards were maintained thereafter. The one exception to this was the gold dollar, minted from 1849 through 1889, the Type I issues of 1849 to 1854 being smaller (13 millimeters diameter) and thicker than subsequent gold dollars of 1854 to 1889 (15 millimeters).