The 1981-S Proof Susan B Anthony Dollar is a United States coin minted from 1979 to 1981, and again in 1999. It depicts women's suffrage campaigner Susan B. Anthony on a dollar coin. It was the first circulating U.S. coin with the portrait of an actual woman rather than an allegorical female figure such as 'Liberty'. The reverse depicts an eagle flying above the moon(with the Earth in the background), a design adapted from the Apollo 11 mission insignia that was also present on the previously issued Eisenhower Dollar. It was one of the most unpopular coins in American history. The coin is often referred to affectionately by collectors as the "Susan B." or "Susie".
The 1981 proof can be the most confusing. On the 1981 the clear "S" is the Type 1 mint mark, and is much more common. Both the Type 1 and Type 2 mint marks are clear, so the difference between them is much more subtle. The top of the Type 1 mint mark is rounded and has a smooth texture, and its top and bottom ends, or serifs, are rounded and rather nondescript. However, the Type 2 is markedly different. The top of the "S" is NOT rounded but flat with a grainy texture and has the same frosty appearance as the portrait. Second, the tips, or serifs protrude. The top serif is the more distended of the two and should be a good indicator when attempting to identify the coin.