Abstract: Raw sheet metal substrate (36) passing through an extrusion die (54) is partially laminated with a thin film of plastic (40). A boundary line (42) is formed between the laminated and unlaminated portions of the substrate (36). The sheet metal substrate (36) is folded upon itself so that the plastic laminate (40) bears in pressing relation against the unlaminated portion of the substrate (36) to create a fold (44) sealed against lateral moisture penetration. The unlaminated portion of the substrate (36) may be chrome plated (50). The extrusion die (54) includes an adjustable die member (64) and an adjustable wear plate (78). Alternatively, the extrusion die (54) may include an adjustable extrusion orifice (62) for varying the thickness of the plastic extruded onto the sheet metal substrate (36). Two sheet metal substrates (36') are moved through the extrusion die (54') simultaneously and in back-to-back relation to neutralize reaction forces from the respective emissions of pressurized plastic.