There are now two different obverse die cracks that have been discovered on a few 2003-S Proof Sacagawea Dollars. One of the die cracks is located at 11:00 and runs from the rim to the portrait. The other die crack (pictured below) that has been discovered is at 1:00 and starts at the edge and runs thru the rim and into the forehead of the portrait.
Die cracks found on proof coins are very rare and are popular with collectors of mint errors. Other proof die cracks have been discovered on coins dated from 2000 thru 2003:
2002-S Jefferson Nickel Obverse Die Crack
2002-S Silver Proof Kennedy Half Dollar Obverse Die Crack
2000-S Silver Proof Massachusetts 25¢ Reverse Die Crack
2003-S Clad Arkansas 25¢ Reverse Die Crack
For additional info and images of other Proof die cracks click here.