Section 42G. The commissioner or his duly authorized assistant may at any time investigate the financial standing and past business conduct of any person applying for or holding a license under section forty-two A, and in such investigation may examine the books of account or other documents or records of any such applicant or licensee, and may take testimony therein under oath; provided, however, that information, disclosed by such investigation and relating to the general business of any such applicant or licensee, but not pertinent to the purposes of sections forty-two A to forty-two J, inclusive, shall be treated by the commissioner as confidential.