16 C.F.R. § 23 app to Part 23
(a) Exemptions recognized in the industry and not to be considered in any assay for quality of a karat gold industry product include springs, posts, and separable backs of lapel buttons, posts and nuts for attaching interchangeable ornaments, bracelet and necklace snap tongues, metallic parts completely and permanently encased in a nonmetallic covering, field pieces and bezels for lockets, and wire pegs or rivets used for applying mountings and other ornaments, which mountings or ornaments shall be of the quality marked.
Note to Paragraph (a): Exemptions recognized in the industry and not to be considered in any assay for quality of a karat gold optical product include: the hinge assembly (barrel or other special types such as are customarily used in plastic frames); washers, bushings, and nuts of screw assemblies; dowels; springs for spring shoe straps; metal parts permanently encased in a non-metallic covering; and for oxfords, coil and joint springs.
(b) Exemptions recognized in the industry and not to be considered in any assay for quality of a gold filled, gold overlay and rolled gold plate industry product, other than watchcases, include joints, catches, screws, pin stems, pins of scarf pins, hat pins, etc., field pieces and bezels for lockets, posts and separate backs of lapel buttons, bracelet and necklace snap tongues, springs, and metallic parts completely and permanently encased in a nonmetallic covering.
Note to Paragraph (b): Exemptions recognized in the industry and not to be considered in any assay for quality of a gold filled, gold overlay and rolled gold plate optical product include: Screws; the hinge assembly (barrel or other special types such as are customarily used in plastic frames); washers, bushings, tubes and nuts of screw assemblies; dowels; pad inserts; springs for spring shoe straps, cores and/or inner windings of comfort cable temples; metal parts permanently encased in a nonmetallic covering; and for oxfords, the handle and catch.
(c) Exemptions recognized in the industry and not to be considered in any assay for quality of a silver industry product include screws, rivets, springs, spring pins for wrist watch straps; posts and separable backs of lapel buttons; wire pegs, posts, and nuts used for applying mountings or other ornaments, which mountings or ornaments shall be of the quality marked; pin stems (e.g., of badges, brooches, emblem pins, hat pins, and scarf pins, etc.); levers for belt buckles; blades and skeletons of pocket knives; field pieces and bezels for lockets; bracelet and necklace snap tongues; any other joints, catches, or screws; and metallic parts completely and permanently encased in a nonmetallic covering.
(d) Exemptions recognized in the industry and not to be considered in any assay for quality of an industry product of silver in combination with gold include joints, catches, screws, pin stems, pins of scarf pins, hat pins, etc., posts and separable backs of lapel buttons, springs, bracelet and necklace snap tongues, and metallic parts completely and permanently encased in a nonmetallic covering.
(e) Exemptions recognized in the industry and not to be considered in any assay for quality of a platinum industry product include springs, winding bars, sleeves, crown cores, mechanical joint pins, screws, rivets, dust bands, detachable movement rims, hat pin stems, and bracelet and necklace snap tongues.
16 C.F.R. § 23 app to Part 23