Necklace This is a Rolex-style diamond crown medallion pendant.

The item shown in the image is a gold-toned crown pendant. It is a style of jewelry often referred to as "iced out" due to being covered in simulated diamonds or cubic zirconia. The pendant features a central crown design and is encircled by a Greek key pattern. This combination of a crown and a Greek key motif is sometimes associated with a style similar to jewelry from the brand Versace. 

The pendant is a hip-hop style medallion. These types of pendants can be made from various materials, including real gold with genuine diamonds, or from more affordable options such as gold-plated stainless steel or sterling silver with cubic zirconia stones. 

Pendants with similar designs are available from several online retailers.