Unadjusted basis; gifts after December 31, 1933

If the property was acquired by gift after December 31, 1933, the basis shall be the same as it would be in the hands of the donor or the last preceding owner by whom it was not acquired by gift, except that for the purpose of determining loss the basis shall be the basis so determined or the fair market value of the property, at the time of the gift, whichever is lower. If the facts necessary to determine the basis in the hands of the donor or the last preceding owner are unknown to the donee, the collector shall, if possible, obtain such facts from such donor or last preceding owner, or any other person cognizant thereof. If the collector finds it impossible to obtain such facts, the basis in the hands of such donor or last preceding owner shall be the fair market value of such property as found by the collector as of the date or approximate date at which, according to the best information that the collector is able to obtain, such property was acquired by such donor or last preceding owner.