An order authorizing investment in bonds issued by any state or of any city, county, city and county, political subdivision, public corporation, district, or special district of any state may authorize the guardian or conservator to select from among bonds issued by any such issuer, without specifying any particular issuer or issue of bonds, if the type of issuer is designated in general terms and the order specifies as to such bonds a minimum quality rating as shown in a recognized investment service, a minimum interest coupon rate, a minimum yield to maturity, and the date of maturity within a five-year range.