661—121.8 (80A) Display of license. Immediately upon receipt of the license issued by the department, the licensee named therein shall cause such license to be posted and at all times displayed in a conspicuous place in the licensee’s principal place of business within the state, so that all persons visiting such place may readily see it. If there is more than one place of business, then there shall be a photocopy of the original license posted in every such place of business. The licensee shall notify the commissioner of each location where a copy of the license is posted. If the licensee has no office in the state of Iowa, the licensee shall post the license at the principal place of business and notify the commissioner of the address where such license is posted. Such license shall at all reasonable times be subject to inspection by the commissioner. It shall be unlawful for any person holding such license to post such license or to permit such license to be posted upon premises other than those authorized therein. Every license, and each copy thereof, shall be surrendered to the department within seven days after written notice to the holder that such license has been revoked. Failure to comply with any of the provisions of this rule is sufficient cause for revocation of the license.