Except as may be limited by the director by rule, a mutual savings bank may invest its funds in obligations of the United States, as authorized by RCW 32.20.030, either directly or in the form of securities of, or other interests in, an open-end or closed-end management type investment company or investment trust registered under the federal investment company act of 1940, as now or hereafter amended, if both of the following conditions are met:

(1) The portfolio of the investment company or investment trust is limited to obligations of the United States and to repurchase agreements fully collateralized by such obligations; and

(2) The investment company or investment trust takes delivery of the collateral for any repurchase agreement either directly or through an authorized custodian.