It will be observed that the prohibition of section 12(a) with respect to certain shipments or deliveries for shipment is confined to those made by producers, manufacturers, and dealers. The terms “producer, manufacturer, or dealer” used in this provision are not expressly defined by the statute. However, in view of the definition of “produced” in section 3(j), for purposes of this section a “producer” is considered to be one who engages in producing, manufacturing, handling or in any other manner working on goods in any State.[5] Since manufacturing is considered a specialized form of production, the word “manufacturer” does not have as broad an application as the word “producer.” Manufacturing generally involves the transformation of raw materials or semifinished goods into new or different articles. A person may be considered a “manufacturer” even though his goods are made by hand, as is often true of products made by homeworkers. Moreover, it is immaterial whether manufacturing is his sole or main business. Thus, the term includes retailers who, in addition to retail selling, engage in such manufacturing activities as the making of slip-covers or curtains, the baking of bread, the making of candy, or the making of window frames. The word “dealer” refers to anyone who deals in goods (as defined in section 3(i) of the Act),[6] including persons engaged in buying, selling, trading, distributing, delivering, etc. It includes middlemen, factors, brokers, commission merchants, wholesalers, retailers and the like.