Many thanks to Master Li's selfless tutorial guidance. 1. Use a 10X magnifier to check if the tiny cracks inside the objectives were infringed with the dye mark, 2. Soak objectives in diiodomethanone, a chemical solution, to test if their relative density is 3.33, and 3. The perfect size scale of oval shape is 3:2:1 for Fei-Cui main stone.