Look for the 1979-P "Wide Rim", 1979-S Proof "Clear S", and 1981-S Proof "Clear S" varieties. The 1999-D business strike is the lowest mintage of the series followed by the 1980-S. The proofs, that where issued in proof sets, have the lowest mintages overall.
Designer: Frank Gasparro
Diameter: 26.50 millimeters
Outer layers - 75% Copper, 25% Nickel
Center - 100% Copper
Weight: 125.02 grains (8.1 grams)
Edge: Reeded (133 Reeds)
Mintmark: "P" (for Philadelphia, PA) on the left side of the obverse, just above Anthony's shoulder
As with many mint mark varieties, it's difficult to tell the difference until you examine them both side by side. No different with the 1981-S Clear S verses the 1981-S Normal S.
As you can see in the images, the S image on the left is a normal or most common mint mark for Susan B Anthony Dollar proofs, and the image on the right is what's called the Clear S variety.
You can see that the normal S is higher relief and appears to almost have a ridge all along it's curves. Also, the bottom serif tends to be flattened on the end, but the clear S is rounded off in the area. Also, the middle area of the Clear S is almost straight across, but the Normal S middle is curving downward.
The normal S tends to be a bit more compact and square, but not all Normal S examples are as obvious as the one imaged on this webpage. So examine each mint mark with care and a good magnifier.
Often, you will find these coins housed behind their proof set plastic and this causes distortions of the mint mark and even the plastic's surface might be damaged, further hampering identification.
If you think you have a Clears S, but not sure, send an image to our email address so we can help: Email:firstname.lastname@example.org