In accordance with this section, a real estate broker shall display a sign at each office and branch office that the real estate broker maintains for the provision of real estate brokerage services. The real estate broker shall display the sign conspicuously on the door or outside of the premises of each office or branch office so that the sign is visible to the public. The real estate broker shall include on the sign the words “real estate” or, where authorized by the respective trade associations, “realtor” or “realtist”.