Code 4150 applies to employers engaged in manufacturing optical goods and ground lenses.  This classification includes specialists who perform precision grinding of lenses or the grinding of blank or rough lenses to curvature and size for retailers, i.e., optometrists and opticians.  This classification also includes the complete process of assembling the lenses into frames to obtain eyeglasses, opera glasses, field glasses and industrial goggles.  Glass and plastic blanks, emery, polishing rouge, steel, silver and gold wire rod or tube, sheet plastic, and metal are received from others.  The glass or plastic blanks are heated; put in molds; formed; annealed; set in grinding machines; ground down to size, gauge, and thickness; centered; polished; and edges are trimmed and beveled.  The lenses are then buffed, washed, and inspected.  Some lenses are shipped to customers, while others are mounted in the product being made.  The products may be manufactured by employers falling within the scope of this classification, or they may be assembled from component parts received from others.