16 CFR §23.4

1. (a)It is unfair or deceptive to represent, directly or by implication, that an industry product is “vermeil” if such mark or description misrepresents the product's true composition.
2. (b)An industry product may be described or marked as “vermeil” if it consists of a base of sterling silver coated or plated on all significant surfaces with gold, or gold alloy of not less than 10 karat fineness, that is of reasonable durability 33 and a minimum thickness throughout equivalent to two and one half (2 1/2) microns (or approximately 100/1,000,000ths of an inch) of fine gold.