This is one of the largest extant Jade(Nephrite) Cong . This type is where the length is longer than the height. Will not comment much on this CONG but can say that among my collection of more than a hundred Liangzhu Culture Jades, this ranks in the top three!!! In Chinese Antique Evaluation - this 'quality' of antique is given the phrase 'BAO JIANG KIA MEN' - roughly translated as 'ONE LOOK AND KNOW IS AN ANTIQUE!!'
To expand your knowledge on Jade especially Liangzhu Culture Jade,please visit the website of the Friends of Jade given in the links. There are many excellent articles in the archives on fake and real Liangzhu Jade.