public static function is_buid($st): bool
  {
    if ( \is_string($st) && (\strlen($st) === 16) && !ctype_print($st) && !ctype_space($st) ){
      $enc = mb_detect_encoding($st, ['8bit', 'UTF-8']);
      if ( !$enc || ($enc === '8bit') ){
        return true;
      }
    }
    return false;
  }