A Dutch-German research team has used a unique method to detect silver shortages in the PV industry. By mapping the silver supply chain from 1995 to 2021, they have identified distinct supply patterns ...
A 1993-made China's videotape help you to become an expert to identify real gold and silver. There are six parts of this video: 1. Appraisal skills and methods of using tools (29 min.) 2. Gold ...
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