(a) 31 CFR part 356 governs the sale and issue of marketable book-entry Treasury securities on or after March 1, 1993, whether held in TreasuryDirect [supreg], Legacy Treasury Direct, or the commercial book-entry system.
(b) 31 CFR part 357 governs holding marketable book-entry Treasury bills, notes, and bonds in the Legacy Treasury Direct system and in the commercial book-entry system.