“ Pursuant to the provisions of section 55 of the Revenue Act of 1928 and section 257 of the Revenue Act of 1926, it is hereby ordered that decisions of the Commissioner of Internal Revenue allowing a refund, credit, or abatement of income, war-profits, excess-profits, estate, or gift taxes, in excess of $20,000, shall be open to inspection in accordance, and upon compliance, with the regulations prescribed by the Secretary of the Treasury and approved by me, bearing even date herewith. ”