Every certificate of license issued shall be posted by the licensee in a conspicuous place easily viewed by the public, in which the licensed business, trade, profession, occupation or activity is carried on, and when such certificate of license has expired it shall be removed from public view. A licensee without a fixed place of business shall have certificates of license in the licensee’s possession while engaged in business. It shall be the duty of each licensee and its agents and employees to whom a certificate of license has been issued to show the same upon demand.