How many ridges does a Susan b Anthony dollar have?

The Susan B. Anthony dollar, which was minted from 1979 to 1981 and again in 1999, has 11 ridges on its edge. These ridges, or "reeding," help prevent counterfeiting and provide a tactile feature for handling the coin. The design features a likeness of Susan B. Anthony on the obverse and an eagle landing on the moon on the reverse.