When bonds issued pursuant to this part have been investigated and certified by any authorized officer of the state and are declared to be legal investments for savings banks, they may be purchased or received in pledge for loans by savings banks, building and loan companies, trust companies, insurance companies, guardians, conservators, executors, administrators, and special administrators, or by any public officer of the state or of any county or other municipal or corporate body in the state having or holding funds which they may legally invest or loan.