Capital gains valuation: treat a prescribed de minimis sale price as deemed cost when acquisition cost is unproven. Where an assessee cannot establish cost of acquisition by satisfactory evidence, the Board directed that the sale price up to a prescribed de minimis amount be treated as the cost for computing capital gains; if the actual cost is satisfactorily proved to exceed that amount, the proved cost must be substituted. The Board clarified that the de minimis amount is a fallback deemed cost and must not be allowed in addition to a proved actual cost, and instructed officers to correct prior misapplication.