The Seiko 5 Sports is a magnificent artifact from July 1970, as confirmed by the serial number 072465. While the Suwa factory was producing the famous 6139, Seiko's Daini division answered back with the Caliber 7017, which was claimed to be the world's thinnest automatic chronograph movement at its release. This early Proof dialed variant captures a bold racing spirit with its matte black dial, prominent orange seconds hand, and a specialized flyback mechanism that allows the timer to be reset and restarted instantly with a single push.

The architecture is quintessentially robust, utilizing a flared tonneau-shaped cushion case that offers a commanding presence on the wrist. The dial features highly legible luminous markers and a rotating inner count-up bezel that provides additional timing functionality. Flipping the watch over reveals the Water 70m Proof" engraving and Daini lightning bolt logo, definitively confirming its authentic Japanese Domestic Market (JDM) heritage and its high-end professional specifications.