The Department of the Treasury acts as fiscal agent for the Commissioner in connection with transactions and operations relating to debentures. Treasury's General Regulations Governing U.S. Securities (31 CFR part 306) and its Supplemental Regulations Governing Federal Housing Administration Debentures (31 CFR part 337) have been and are adopted as revised and amended, to the extent applicable, as the regulations of the Commissioner governing the issuance of, transactions in and redemption of debentures, including the payment of interest thereon with the following exceptions:

(a) Payment of final interest on maturing or called debentures. If the notice of maturity or call for redemption shall so provide, the final installment of interest payable on any debentures at maturity or earlier redemption date may be paid with the principal in accordance with the assignments on the debentures instead of by separate check drawn to the order of the registered payee and forwarded to him at his address of record.

(b) Closing of transfer books. If the call for redemption shall so provide, the books maintained by the Treasury Department may be closed against transfers and denominational exchanges in debentures for three full months preceding any interest payment date with respect to any debentures called for redemption on such interest payment date.