Section 53. Any mutual liability insurance company authorized to do business in this commonwealth may with the approval of the commissioner of insurance distribute its risks into groups in accordance with the nature of the business and the degree of the liability of injury and with like approval fix by and for such groups in accordance with the experience of each group all premiums, assessments and dividends; but all the funds of the company both actual and contingent shall be available for the payment of any claim against the company.