A mutual savings bank may invest its funds in the valid warrants or bonds of any county, city, town, school district, port district, water-sewer district, or other municipal corporation in the state of Washington issued pursuant to law and for the payment of which the faith and credit of such county, municipality, or district is pledged and taxes are leviable upon all taxable property within its limits.
A mutual savings bank may invest its funds in the water revenue, sewer revenue, or electric revenue bonds of any city or public utility district of this state for the payment of which the entire revenue of the city's or district's water system, sewer system, or electric system, less maintenance and operating costs, is irrevocably pledged.