Section 40. No person, except a producer or dealer selling milk to other than consumers, or selling not more than twenty quarts per day to consumers, shall deliver, exchange, expose for sale or sell or have in his custody or possession with intent so to do any milk or cream in any town where an inspector of milk is appointed, without obtaining from such inspector a license which shall contain the number thereof, the name and place of business. A license issued to a partnership or corporation shall be issued in the business name of said partnership or corporation and shall contain the names in full of the partners and managers of said partnership or officers of said corporation. The license shall, for the purposes of sections forty to forty-two, inclusive, be conclusive evidence of ownership and shall not be sold, assigned or transferred. No person, other than a producer selling milk or cream, or both, shall display the word ''dairy'' on any vehicle used by him or his authorized agent in the business of selling milk or cream, unless such person has a license, in full force and effect, issued under section forty-eight A. Whoever in such a town engages in the business of selling milk or cream from any vehicle for household deliveries shall display conspicuously on the outside of each vehicle so used the name and principal place of business of the licensee in Gothic letters not less than one and one-half inches in height. Whoever in such a town engages in the business of selling milk or cream in a store, booth, stand or market place shall have his license conspicuously posted therein.