Gold-filled pieces are made by combining a layer or layers of gold alloy to a base metal (usually brass). Than the metal is rolled to the desired thickness and shape. Gold-filled parts can be 12KT or 14KT. Gold-filled items can be worn by most people without alergic reactions or dificulties.
Gold-finished and Silver-finished items are also called gold color and silver color. Base metal (brass or steel) is electroplated with a non-standardized thickness of gold, silver and nickel.
Gold-plated, silver-plated, nickel-plated
Gold-plated, silver-plated and nickel-plated products are base metal items plated with an industry standard 0.15 to 0.25 mils layer of gold, silver or nickel.
Karat is the measure of how pure the gold is. 24KT is pure gold. 14KT is 14 parts of gold and balance is alloy. Standard gold fineness in US is 14KT.
Nickel Silver items are made of an alloy containing nickel with sterling silver in color, with a greyer tone.
Niobium items are made of a hypo-allergenic metal which is naturally grey base metal. Niobium is anodized to create six signature colors. Most metal-sensitive people can comfortably wear niobium. Niobium was first engineered to protect hypersonic aerospace vehicles from extreme conditions.
Sterling silver products are made of 92.5% pure silver and 7.5% copper or other alloy. These proportions are fixed by law and sterling silver items must have embedded "925" hallmark.
Titanium items are made of neutral grey, lightweight metal. After manufacturing into desired shape, the neutral grey base metal titanium can be anodized into six colors. Titanium is not certified as hypo-allergenic, but most metal-sensitive people can wear these products comfortably.
Vermeil items are made of sterling silver, heavily electroplated with 18KT or 22KT yellow gold.