Tickets and stubs of every description sold or unsold, other than unsold reel tickets, used for any boxing contest or wrestling exhibition shall be removed to the commission district office for audit, if necessary, by a representative of the commission after the promoter and representative have completed computation of gate receipts and taxes due thereon. In the event tickets are not taken by a commission representative they shall be retained by the promoters for a period not to exceed six months. Such tickets may be destroyed after they have been held for at least 30 days and written permission has been granted by the commission for the destruction of such tickets. Tickets shall be kept in separate packages for each show in order that an audit can be made at any time by the commission.