Get a manufacturer to make you a pressed CD using glass as a base layer and gold as the reflective layer. Glass CDs are actually a thing[1], and a gold reflecti

Get a manufacturer to make you a pressed CD using glass as a base layer and gold as the reflective layer. Glass CDs are actually a thing[1], and a gold reflective layer should not complicated the production that much. I'd actually expect such a CD to last tens of thousands of years. For your requirement of 100 to 200 years, a pressed (not burned) CD might well be sufficient if the storage conditions are optimal (cool, dry, no oxygen). [1] https://www.engadget.com/2006-10-22-near-perfect-glass-cd-hits-stores-in-akihabara-shibuya-for-831.html https://www.engadget.com/2006-10-22-near-perfect-glass-cd-hi...