31 CFR § 330.6 - Securities eligible for special endorsement.
(a) General authority. A qualified agent is authorized to affix the special endorsement to:
(1) Savings bonds of Series A, B, C, D, E, EE, and I and savings notes to be redeemed for cash; and
(2) Eligible savings bonds of Series E and EE and savings notes to be redeemed in exchange for Series HH bonds under the provisions of Circular No. 2–80 (31 CFR part 352).
(b) Securities which may not be specially endorsed. The special endorsement procedure may not be used in any case in which payment or exchange:
(1) Is requested by a parent on behalf of a minor child named on the security, or
(2) Requires documentary evidence, under regulations contained in Circulars Nos. 530 and 3–80 (31 CFR parts 315 and 353, respectively), except as indicated in § 330.5.
(c) Securities owned by nonresident aliens. As securities owned by a nonresident alien individual, or a nonresident foreign corporation, partnership, or association, may be subject to the nonresident alien withholding tax, bonds and notes held or received by an agent for the account of such owners must be forwarded to a TRS Site for redemption, even though the agent may specially endorse the securities.