Section 117C. After notice of the establishment of grades and standards and the determination of brands or labels as provided in the two preceding sections, it shall be unlawful to use an official grade designation in connection with the sale of such farm products without using the brand or label determined as aforesaid for such grade and standard, or to use such a brand or label unless the farm product bearing the brand or label is in fact of the grade or standard so established, or to use such a brand or label before the authorization of the use of, or after the revocation or during suspension of the right to use, such brand or label, by the commissioner. Any violation of this section shall be punished for a first offence by a fine of not more than fifty dollars and for a subsequent offence by a fine of not more than two hundred dollars. Whoever obstructs or hinders the commissioner or any of his assistants in the performance of his duties under sections one hundred and seventeen A to one hundred and seventeen F, inclusive, shall be punished by a fine of not less than ten nor more than one hundred dollars.