Are you asking what zztc on jewelry means? Jewelry appraisal agency. ZZTC is a third-party authoritative jewelry product quality inspection and testing institution authorized by Guangdong Provincial Bureau of Quality and Technical Supervision to Guangdong Zhongzheng Jewelry Appraisal Co., Ltd. The center has CMA inspection qualification certificate and is an impartial and independent third-party jewelry inspection and testing institution. The report and certificate issued by it have legal effect.