When looking to buy double eagles in terms of gold coin offerings, there are several things you should look for. You will want to invest in double eagles that have specific markings on them that give an indication as to their true authenticity. Several characteristics can be identified in double eagles that you should be able to easily spot.
The Coronet Liberty head double eagles were crafted between the years 1849 and 1907. These coins were minted with a value of twenty dollars in every case, but some were not crafted with the motto “In God We Trust,” while other double eagles were crafted with the motto included. Look for double eagles with no motto on the coin with dates between 1849 and 1866. After 1866, if the coin is authentic, it will have the motto on the coin.
When looking at double eagles that have the traditional Saint Gaudens design, these coins should have dates that fall between 1907 and 1933, excluding the years 1917, 1918, and 1919 because no coins were made during those years. The 1907 double eagles with the Saint Gaudens design were minted without a motto on them, as well as coins in 1908; the 1907 double eagles were made with a high relief and the 1908 coins were made with a low relief. In 1907, the double eagles also had Roman numerals; a year later this changed to Arabic numbers. There are some coins dated 1908 that do include the motto as well as Arabic numbers and these double eagles are definitely genuine.
Bear in mind that while there are a few 1933 double eagles available, they are illegal to sell and illegal to own; this is because a stoppage was placed on the making of such coins, and shortly thereafter there was a theft of double eagles dated 1933. Impressively rare, these coins are high priced, but are sometimes unlawful to trade. You will need to be careful when getting a 1933 piece; some coin collectors might have gotten 1933 double eagles lawfully, but the supply is limited.