Any end product manufacturer who is a retail baker shall be exempt from the provisions of this chapter. For the purposes of this section, the term “retail baker” shall be deemed to include all end product manufacturers who sell end products directly to the ultimate consumer: Provided, That such term shall not include any end product manufacturer who derives less than 10 per centum of gross end product sales revenues from sales to ultimate consumers or who derives 10 per centum or more of gross food or food products sales revenues from the sale of such products manufactured or produced by others.