According to Panerai, the https://www.xhorloge.com/product-categorie/iwc/ key to this characteristic is the https://www.xhorloge.com/ composition of the alloy, which is 75% gold, 24% copper (whose presence you'd expect due to the material's deep red coloration), but also a small amount of platinum (0.4%). It's this hint of platinum matched with a high concentration of copper – a ratio https://www.xrelojes.com/ fine-tuned at Panerai's Laboratorio di Idee – that accounts for what Panerai describes as its "unique tone and an extreme degree of mechanical and oxidation resistance."