In addition to the investments permitted by § 4-5-6, any public funds which are not needed for current operating expenses may be invested in:
The investments shall be registered in the name of the political subdivision or authority or held under a custodial agreement at a bank. The investments shall be rated at the time of purchase within the two highest general classifications established by a rating service of nationally recognized expertise in rating bonds of states and their political subdivisions. Other than permanent, trust, retirement, building, and depreciation reserve funds, such securities as provided in subdivisions (1) and (2) shall mature with eighteen months from the date of purchase or be redeemable at par at the option of the holder within eighteen months from the date of purchase.
Moneys in any bond redemption fund may be invested only in the types of investments listed in § 4-5-6. The investments shall be due and payable on or before the date when the bonds for the payment of which the bond redemption fund was created become due and payable, except bonds of the United States redeemable at par.
No restriction in this section limits the investment authority otherwise granted under the laws of this state.
SDCL 4-5-6.2