31 CFR §306.115

For the purposes of this subpart, the definitions provided in 31 CFR 357.3 are applicable, with the following additions: Definitive Treasury security means a Treasury bond, note, certificate of indebtedness, or bill issued under 31 U.S.C. chapter 31 in engraved or printed form. Eligible book-entry Treasury security means a security maintained in TRADES that was originally issued prior to August 15, 1986, which by the terms of its offering circular is available in either definitive or book-entry form.