Rare, beautiful condition. There is no peeling of the outer case protector or corrosion of the hands, which are common issues with old tuna cans. The bezel also rotates crisply and smoothly (the bezels of divers from this era rotate in both directions). Seiko Professional Diver 600m Tuna Can 7549-7000 Quartz Working Genuine urethane belt Valuable genuine gold buckle The battery replacement time is unknown, but it is currently working well (I've heard the battery life is about 5 years). This is the Seiko Professional Diver 600m, commonly known as the "Tuna Can." It is the successor to the "6159-7010," a 600m saturation diving specification automatic professional diver released in 1975, which was the world's first titanium case. This model, equipped with the world's first quartz movement, was released around 1978. The unique, round, large case has a powerful presence. A practical day-date display is located at the 3 o'clock position, and quick changes are possible with the first pull of the crown. With a quartz movement and hacking function, it is also recommended for daily use. The back cover is engraved with the "sea wave," the symbol of Seiko divers. This model is essential in the history of Seiko divers, which are called the "guardians of the deep sea" due to their high reliability. While well-maintained, working examples are becoming increasingly rare, it's a wonderful watch that only enthusiasts will appreciate! It's a fairly large watch, but it can be worn lightly thanks to the lightweight titanium case and ceramic outer case.