An entity that may invest pursuant to section 15A or the legal list may invest in the capital stock of any insurance company that may conduct a fire and casualty insurance business; provided, however, that no insurance stock shall be purchased if the cost of the insurance stock added to the cost of insurance stocks and bank stocks already owned shall exceed 66 2/3 per cent of the total of the assets of the entity.
Mass. Gen. Laws ch. 167, § 15j