>>23224417A common item, a sterling silver figaro chain. The item weighs 6.5 grams, and has roughly 0.1933 troy ounces of silver content. It is worth about $8.
A dealer will pay about 75% of the value of this sort of scrap, so this item should bring around $6 to a seller.
Note the black streaking tarnish across the surface. A costume, silver plated item, in addition to wear points at the corners, would be more highly polished, and likely would have been coated in lacquer, to prevent wear. So the silver woupd not have the opportunity to tarnish.
This is an indicator, along with, again, the mate finish stamping, and the shape of the end bales on the chain.