Section 21. Sealers shall inspect at least semiannually all cans, moulds or other containers sealed in accordance with the preceding section, and shall make a record of such inspection. If a container has once been sealed as aforesaid, it shall not be necessary to have it sealed again while it is used for the sale of ice cream or other frozen desserts and/or frozen dessert mix as long as it remains in the same condition as when first sealed.