JMZ should be the abbreviation of the full name of the factory that made this necklace.

Just because a counter sells many jewelry brands doesn't necessarily mean it has its own factory.

These companies have their own suppliers.

JMZ should be Kim Myung Soo Jewelry Co., Ltd. ..

golden

Gold is a simple form of chemical element gold (chemical element symbol Au), which is a soft, golden yellow and corrosion-resistant precious metal.