39 CFR § 761.3 - Scope and effect of book-entry procedure.
(a) A Reserve Bank as fiscal agent of the United States acting on behalf of the Postal Service may apply the book-entry procedure provided for in this part to any Postal Service securities which have been or are hereafter deposited for any purpose in accounts with it in its individual capacity under terms and conditions which indicate that the Reserve Bank will continue to maintain such deposit accounts in its individual capacity, notwithstanding application of the book-entry procedure to such securities. This paragraph is applicable, but not limited, to securities deposited:
(2) By a member bank for its sole account;
(3) By a member bank held for the account of its customers;
(4) In connection with deposits in a member bank of funds of States, municipalities, or other political subdivisions; or,
(5) In connection with the performance of an obligation or duty under Federal, State, municipal, or local law, or judgments or decrees of courts.
(b) A Reserve Bank as fiscal agent of the United States acting on behalf of the Postal Service may apply the book-entry procedure to Postal Service securities deposited as collateral pledged to the United States under Treasury Department Circulars Nos. 92 and 176, both as revised and amended, and may apply the book-entry procedure, with the approval of the Secretary of the Treasury, to any other Postal Service securities deposited with a Reserve Bank as fiscal agent of the United States.
(c) Any person having an interest in Postal Service securities which are deposited with a Reserve Bank (in either its individual capacity or as fiscal agent of the United States) for any purpose shall be deemed to have consented to their conversion to book-entry Postal Service securities pursuant to the provisions of this part, and in the manner and under the procedures prescribed by the Reserve Bank.
(d) No deposits shall be accepted under this section on or after the date of maturity or call of the securities.