This timepiece is a masterpiece of technical engineering built for saturation diving- not just a watch, but a highly specialized tool used by professionals. The Seiko Professional Diver 600m, reference 7C46-6010, is entirely made of Titanium, making it significantly lighter and more corrosion-resistant than stainless steel equivalents. It is nicknamed the "Ashtray" due to the unique, rounded, notched design of its unidirectional bezel, which resembles a typical office ashtray of the time.

The heart of the watch is the ultra-robust Seiko Caliber 7C46 quartz movement, which is designed for high-torque and long-term serviceability in professional environments, featuring an End-of-Life (EOL) battery indicator. This model is distinguished by its black dial contrasted with clear white hands and markings, ensuring extreme legibility even at depth. This is a must-have for any serious collector of vintage tool watches, particularly those who appreciate pioneering quartz diver technology and the heritage of the Seiko Tuna line.