Section 8. No license shall be suspended or revoked except after hearing thereon by the commissioner or such of his assistants as he may designate. The commissioner shall give the licensee at least ten days' written notice, in the form of an order to show cause, of the time and place of such hearing by registered mail addressed to the principal place of business in this commonwealth of such licensee. The said notice shall contain the grounds of complaint against the licensee. Any order suspending or revoking such license shall recite the grounds upon which the same is based. The order shall be entered upon the records of the commissioner and shall not be effective until after thirty days' written notice thereof given after such entry forwarded by registered mail to the licensee at such principal place of business. No revocation, suspension or surrender of any license shall impair or affect the obligation of any lawful retail instalment contract acquired previously thereto by the licensee. Within thirty days after such suspension or revocation the person aggrieved thereby may appeal to the superior court for the county of Suffolk, sitting in equity. The court shall hear all pertinent evidence and determine the facts, and upon the facts as so determined review said suspension or revocation and, as justice and equity may require, affirm the same or order that the commissioner rescind it.