When it comes to vintage Grand Seiko and the Grand Seiko 5646-7040, the famous designer Taro Tanaka comes to mind. Tanaka was credited with developing a set of rules in 1962, called the “Grammar of Design”, emphasizing the concept of a unified design within Seiko. Ultimately, he wanted to compete with the Swiss watchmakers in producing standout luxury watches. The Grammar of Design emphasized nine elements in total including multi-faceted markers and hands, highly polished bezels and curved sidelines. This design philosophy remains the essence of the brand today.

The 56GS was the last vintage Grand Seiko mechanical series, mass produced from 1970 to 1974 in a wide variety of models. The production process of the 56GS series was partially automated and used the 5646 28,800bph movement, which provided the right balance of accuracy and reliability. Grand Seiko had previously introduced higher precision models, with a movement speed of 36,000bph, but such high frequency can come at the expense of reliability.

Among the models released as part of the 56GS series is the 5646-7040, a relatively rare model as it was the only vintage mechanical Grand Seiko with Arabic numerals. It also features unique textured finishes on both the dial and bezel. The Arabic numerals are perfectly polished and reflect light from any angle, giving the dial an ever changing look. This watch has a case diameter of 35.5mm, and a relatively short 39mm lug to lug size. As such, it may be considered quite small. On the other hand, with a reliable automatic movement and a quickset day/date function, it can be worn on a daily basis.

The Grand Seiko 5646-7040 was only produced for one month in June 1973 and can be difficult to find in good condition. This model is far removed from the Grammar of Design rules and is a real oddity among vintage Grand Seikos, and that’s exactly what makes it so special.