The Seiko Prospex SRP637 is nicknamed the Baby Tuna. The protective shroud on this model is made from stainless steel and it increases the case diameter slightly to 46.5mm. The screw-down crown is now offset at the four o’clock position. Inside the case is the 24-jewel Seiko caliber 4R36 automatic (self-winding) movement that hand winds and is hackable. The powerful Seiko LumiBrite luminescent material used on the hands and markers gives the watch the same brilliant glowing properties that made the Seiko Monster such a huge phenomenon.

Lug width is 22mm. Case size is 46.5mm. Slightly domed Hardlex mineral crystal. Concave uni-directional rotating dive bezel helps protect the crystal. Seiko stainless steel bracelet with dual push-button deployant clasp (and diver extension). Solid screw-in case back. Water resistant to 200 meters. Day and date window.