Each licensee under this chapter shall at all times retain in his possession the license issued by the city clerk and each person issued an identification card under this chapter shall retain the same in his personal possession at all times while engaged in the activity so licensed within the city and shall produce and show it on the demand of any person solicited or of any police officer or official of the city. No licensee or person issued an identification card shall alter, remove or obliterate any entry made upon such license or card, or deface such license or card in any way. Each license and card shall be personal and not assignable or transferable, nor shall any license or card be used by any person other than the licensee or the person for whom issued. (Prior code § 17-11)