Example:
D600AST1B
AKAA0022BPMW
Y5689460375
Line 1:
D600AST1B
The first letter indictates what kind of processor it is.  You can probably guess that its a Duron from the 'D'.  The following 3 or 4 numbers are its clock speed.  This one is 600MHz.  The remaining letters and numbers indicate some other info.  I hear that you can determine if the chip is OEM or not by looking at it, but I don't really know.
Line 2:
The 4 digits in the middle indicate when the ship was produced.  The '00' indicate the year 2000, the '22' indicates Week 22.
Line 3:
Dunno.  You tell me.