Seiko Prospex SRP637K1 Baby Tuna Vs Seiko SRP307 “Monster”

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Seiko Prospex SRP637K1 Baby Tuna
A new Baby Tuna has been added to the core line up of Seiko's newly globally launched Prospex series! The SRP637 is the featured model today, but there will actually be two styles to choose from. The SRP637 is a stainless steel case, bracelet and shroud that measures out at 46.5mm wide. The piece has a 60 minute uni-directional rotating bezel. The shroud on this model, unlike last years LE baby tuna, is also in stainless steel as I previously mentioned. The crown is located at the 4:00 position, in order to eliminate the possibility of interfering with your wrist. The steel bracelet will use a pin and collar system for sizing, and has plenty of micro adjustments on the clasp. There is also a folding expansion for the clasp in order to add length for going over a wet suit. The movement used is Seiko's self-winding 4R36 automatic, with 21,600 bph, 24 jewels, a 41 hour power reserve, and both hack and hand wind feature. This will have a closed case back but does of course have 200m water resistance. The crystal is Seiko's hardened mineral called Hardlex for shatter resistance. The Lumibrite luminous is applied heavy to all three hands and all index markers, creating excellent legibility in dark situations.

Seiko SRP313K1 “Monster”
The Seiko Monster is quite possibly the perfect automatic. It’s certainly wearable and then some, year round.

True dive watches with a 200 m water resistance rating, a beefy case & screw down crown, good lume and a toothy rotating bezel– the Monsters are pretty much legends in the watch community at large. The fact that they’re so affordable also helps.

The most impactful change is in the movement. The new option is hackable (the seconds hand stops when you pull the crown out fully, meaning you can set a more precise time)… and you can hand wind it at the crown. Alright, so it’s not THAT big of a deal, but if you wear multiple watches during the week, chances are one or more of your automatics will stop (assuming you don’t use a watch winder). Hand-winding is a good way to kick start them once they’ve run out of power, or, to make sure they’ll make it through the night if you haven’t worn it that day.