protected function _isProductVoucher()
    {
        $oDb = \OxidEsales\Eshop\Core\DatabaseProvider::getDb();
        $oSeries = $this->getSerie();
        $sSelect = "select 1 from oxobject2discount where oxdiscountid = " . $oDb->quote($oSeries->getId()) . " and oxtype = 'oxarticles'";
        $blOk = ( bool ) $oDb->getOne($sSelect);

        return $blOk;
    }