Seiko Prospex Marinemaster Diver 300M SLA021

The Seiko Prospex Marinemaster SLA021J1 is one of Seiko's most iconic diving watches. For many people this series welcomed Seiko in the high-end diving watch world - with good reason - and this latest model pushes the bar even higher. The finishing level, the specifications and the overall feel are absolutely top notch.

To start, the movement. It's the Seiko Cal. 8L35, based on the Grand Seiko 9S55. A beautiful, 28,800bph movement with 50 hours of power reserve and specifications of +15/-10 seconds per day. A truly amazing, in-house movement that does justice to a watch in this class.

The watch itself, with its monobloc case, is very elegantly shaped, nicely fitting around your wrist. While the initial 44.3mm diameter may put you off a little bit, the placement of the crown and the relatively manageable 50mm lug to lug distance ensure it's not a goliath and will fit most wrists. The watch is purpose built, so very legible and using durable materials such as a ceramic for the bezel and a sapphire crystal to protect the dial. The bracelet also feature's a diver's extension, in case you want to wear this beauty over a wetsuit, when you take it to the 300m depth it can resist.

Ref: SLA021

Dated: 2025

Bracelet: Stainless Steel Bracelet and Black Rubber Strap

Case: 44.3mm x 15mm Thickness - Stainless steel

Bezel: Ceramic

Movement: 8L35 - Automatic

Functions: HMS, Date

Box and Papers: Inner/outer boxes, and warranty card

Crystal: Sapphire

Bracelet size: 7.75”

Case has no wear. Bracelet has no wear. Dial, hands, and crystal have no wear.