Interests in any open-end registered investment company registered under the federal Investment Company Act of 1940, provided that the portfolio of any such company is limited to securities and investments authorized for investment by representatives in Sections 21-1.01 through 21-1.06 of this Act and to agreements to repurchase such obligations, which agreements, with respect to principal and interest are (1) at least 100% collateralized by such obligations marked to market on a daily basis, and (2) the investment company takes delivery of such obligations either directly or through an independent custodian. To the extent that such investment company engages in when issued or delayed delivery transactions, it may do so only as a part of its normal security acquisition practices and not as a means of speculating on interest rates.