The Commissioner may, of his own motion or on application, call for and examine the records of any proceedings under this Act before any person appointed under section 4 to assist the Commissioner and revise after such inquiry as he may deem necessary any order passed in such proceedings:
     Provided that no order prejudicial to a dealer shall be passed ¹[under this section] without giving him a reasonable opportunity of being heard:
     Provided further that the Commissioner shall not revise any order under this section in any case--
         (a) where an appeal against the order lies to the prescribed authority, the time within which such appeal can be made has not expired or the dealer has not waived his right to appeal to the prescribed authority;
         (b) where the order is the subject of an appeal before the prescribed authority;
         (c) where the application is made by an aggrieved dealer for such revision unless the application is made within ninety days from the date on which the order was served on the applicant;
         (d) where the order is sought to be revised by the Commissioner of his own motion, if such order was made more than two years previously.