What is stamped 526 with triangles on ring?

The stamp "526" on a ring typically indicates the metal's purity, often referring to a specific alloy or quality, such as sterling silver, which is 92.5% pure silver. The triangles could signify a specific brand or designer, or they may represent a hallmark indicating the manufacturer or origin of the piece. To get a more accurate identification, it's advisable to consult a jeweler or appraiser familiar with jewelry markings.