The Commissioner of the Fiscal Service, as designee of the Secretary of the Treasury, may waive or modify any provision or provisions of these regulations. He may do so in any particular case or class of cases for the convenience of the United States or in order to relieve any person or persons of unnecessary hardship:

(a) If such action would not be inconsistent with law or equity, (b) if it does not impair any existing rights, and (c) if he is satisfied that such action would not subject the United States to any substantial expense or liability.

The Commissioner of the Fiscal Service, as designee of the Secretary of the Treasury, may require

(a) Such additional evidence as he may consider necessary or advisable, or

(b) A bond of indemnity, with or without surety, in any case in which he may consider such a bond necessary for the protection of the interests of the United States.

Nothing contained in these regulations shall be construed to limit or restrict existing rights which holders of savings bonds previously issued may have acquired under circulars offering the bonds for sale or under the regulations in force at the time of the purchase.

The Secretary of the Treasury may at any time, or from time to time, prescribe additional, supplemental, amendatory, or revised rules and regulations governing the United States Savings Bonds and Savings Notes to which this circular applies.