A carved white jade 'dragon and phoenix' vase and cover mark and period of Qianlong

the pear-shaped vase with waisted neck and flared mouth, flanked by a pair of qilong scroll handles, the four-character mark incised in a single horizontal line below the rim, finely carved in high-relief with a scaley dragon clambering around the sides in pursuit of a flaming pearl, resting on the back of a resplendent phoenix, standing tall with a loose ring in its beak, the long curling feathers to both wings and tail individually detailed in high-relief, the domed cover to the vase surmounted by a bead finial