“ The company insists that the term 'fair average value of its capital stock' means fair average value of the aggregate shares of its stock and not the value of the corporate assets; that the fair average value of the shares, based upon bona fide sales of the stock in reasonable volume, was correctly stated in its return; that the aggregate value of the shares so determined by the fair average selling price of the individual shares must be adopted as the single standard for determining the value of the capital stock ”

“ As the method to be pursued in ascertaining the value is not prescribed, we think that it was left to the sound judgment and discretion of the Commissioner, subject only to the obligation to take into consideration every relevant fact. ”