Intaglio
in·ta·glio | in-ˈtal-(ˌ)yō
noun
A design carved down into a gemstone, often used for seals. Devices which made an impression in wax used to seal a letter or authenticate a document
Intaglio refers to a type of design that is fashioned within a gemstone or another precious piece of jewelry or metal. The resulting design was historically used for seals to authenticate documents or impress upon letters to show the provenance of the letter’s writer. Intaglio is still commonly used on watch fobs. Historically, fobs were used in conjunction with a seal, and the historical tradition of carving a design to the end of the fob remains. The most common substance into which intaglios are carved is a type of quartz known as Carnelian. There are several other iterations of the same technique, however.