Bullshit. Who merged? Who does he think he is? I'm obviously fooling you. NGTC is the most authoritative national gem quality testing center. NGSTC is the testing center for gold and silver products. NGDTC is the quality inspection center of gold products. You got it? They just come to make "sticky sticks", as can be seen from their names, much like NGTC. As a result, many merchants say "national inspection" to customers, and NGTC and NGDTC are also national inspections. In fact, this is a confusing practice. NGSTC is the "Gold and Silver Products Quality Supervision and Testing Center" and NGDTC is the "Gold Products Quality Supervision and Testing Center". Did you find out? It has nothing to do with jewelry and diamonds, so it is self-evident how credible their testing certificates can be.