31 CFR 328.6 - Requirements for endorsement.
(a) On bearer securities. The endorsement must be imprinted in the lefthand portion of the face of each security with the first line thereof parallel to the left edge of the security and in such manner as to be clearly legible and in such position that it will not obscure the serial number, series designation, or other identifying data, and cover the smallest possible portion of the text on the face of the security. The dimensions of the endorsement should be approximately 4 inches in width and 1 1/2 inches in height, and must be imprinted by stamp or plate of such character as will render the endorsement substantially ineradicable. The name of the Federal Reserve bank of the district must appear on the plate or stamp used for the imprinting of the endorsement, and presentation to the appropriate branch of the Federal Reserve bank named will be considered as presentation to the bank. When securities are to be presented to the Bureau of the Fiscal Service, the words “United States Treasury” should be used in lieu of the words “Federal Reserve Bank of _______, Fiscal Agent of the United States.” No subsequent endorsement will be recognized. If the form of endorsement on a security is different than that prescribed in § 328.5, the provisions of §§ 328.7 and 328.8 shall not apply to the security.
(b) On coupons. Unmatured coupons attached to restrictively endorsed securities should be canceled by imprinting the prescribed endorsement in such manner that a substantial portion of the endorsement will appear on each such coupon. If any such coupons are missing, deduction of their face amount will be made in cases of redemption, and in cases of exchange, remittance equal to the face amount of the missing coupons must accompany the securities. All matured coupons, including coupons which will mature on or before the date of redemption or exchange (except as otherwise specifically provided in an announcement of an exchange offering), should be detached from securities upon which restrictive endorsements are to be imprinted.