If the director finds that avocados which are being prepared for market conform to the applicable standards, he shall so indicate by an official stamp placed on each flat, carton, or any other container by, or under the supervision of, the inspector, stating that the applicable standards have been complied with on the date of pack. Except as provided in this chapter or regulations of the director, it is unlawful for any person to ship to market or otherwise place into the channels of trade any container of avocados which does not bear the official stamp placed thereon pursuant to the provisions of this chapter and regulations promulgated pursuant to this chapter.