Pinchbeck, also referred to as "Pinch," was created in the seventeenth century by Christopher Pinchbeck. Pinchbeck is an alloy--a mixture of copper and zinc--that was used extensively in the art of jewelry making as an inexpensive, but appealing gold substitute. By the mid-nineteenth century, however, the use of Pinchbeck diminished greatly due to the legalization of 9 karat gold. Identifying Pinchbeck is a tricky process unless you know a few specific facts about the piece you are trying to identify.
Determine the age of the jewelry. If the piece of jewelry in question was produced prior to 1840, then it could be pinchbeck. Pinchbeck was rarely used after the mid-nineteenth century.
Determine the how the piece was used. Pinchbeck was used primarily for mourning or sentimental pieces of jewelry, such as lockets, broaches and frames for cameos. If possible, ask the owner if they know any history about the piece of jewelry. Many mourning pieces were made to memorialize the passing of a loved one. If the piece is determined to be mourning or sentimental jewelry and was produced before 1840, it could be pinchbeck.
Examine the finish. Pinchbeck resembles gold in normal light, but when held up and examined closely in natural light, it gives off a coppery glow. Also, because of its alloy properties, a piece of pinchbeck will show signs of wear and tear, such as flakes, tarnish, greening or dents.