17 CFR 260.4a-3: a-3 Exempted securities under section 304(a)(9).

The provisions of the Trust Indenture Act of 1939 shall not apply to any security which has been or is to be issued under an indenture which limits the aggregate principal amount of securities at any time outstanding thereunder to $10,000,000 or less, but this exemption shall not be applied within a period of thirty-six consecutive months to more than $10,000,000 aggregate principal amount of securities of the same issuer.