The ASFST serial number is next to the CE mark and underneath
the barcode at the bottom of the instrument case.  Newer versions
of the rubberized grip have a cut-out so you can see the serial
number.

  

For older versions of the rubberized grip, you will
need to remove the grip to see the serial number
of the instrument.

  

NOTE:  There is another white sticker on the other side of the device - this "F Number" is an Intoximeters internal designation and is NOT a serial number.