JSP Gold & Precious Metal Testing

Sooner or later a beach hunt turns up a ring with no hallmark, and guessing is how people end up selling 18k for scrap. A test stone and a set of acids gives you an answer in under a minute: rub a streak, apply the acid for the karat you are testing, and watch whether it holds or dissolves. JSP's kits cover 10k through 22k plus silver and platinum, and the neutralizer is worth having on hand for cleaning the stone and dealing with spills. Store the acids sensibly, because that is exactly what they are.