/ECO_LEVEL=characters
  /NOECO_LEVEL

   The /ECO_LEVEL qualifier is used to select the specific ECO
   when reading the appropriate symbol table files.  It is used
   in conjunction with the /VERSION qualifier.

   If /ECO_LEVEL is absent from the command line, the tool will
   search the patch and build areas for symbol table files which
   match the link date and time of the loaded driver.

   If you wish to select the version from the base directory
   (i.e. the SSB kit), you should enter the /NOECO_LEVEL
   qualifier.