Seiko SPB155 Men’s Alpinist Automatic Watch

A Heritage Reborn – Design & Aesthetic

We present the SPB155: a modern reimagining of Seiko’s 1959 sport watch, part of the Prospex Alpinist line. This version retains the spirit of its forebear while embracing contemporary tastes. The case is modestly downsized to 38 mm in diameter, which lends it versatility on the wrist, while its curved sapphire crystal—complete with inner anti-reflective coating guards the gradient green dial with clarity and elegance. The dial’s hues shift subtly, drawing the eye, with date display, luminous hands, and markers finished in Seiko’s LumiBrite for visibility in dim light.

Mechanical Credentials

Driving the SPB155 is Seiko’s own automatic calibre 6R35, a 21-jewel movement beating at 21,600 vibrations per hour. It offers a generous ~70 hours of power reserve, and supports both automatic and manual winding. With this movement, Seiko balances robust performance with reliable daily usage.

Build, Case, and Wearability

Constructed in stainless steel, the watch features a screw-down crown and a see-through case back. The case thickness is 12.9 mm, with a lug-to-lug length of 46 mm, giving wearers a presence without excess bulk. The bracelet is also stainless steel, fitted to 20 mm lugs, and secured via a tri-fold push-button release clasp for both comfort and security.

Durability & Practical Features

Seiko has outfitted the SPB155 with water resistance rated at 20 bar (200 meters / ~660 feet), which ensures suitability for swimming, snorkeling, and daily wear in wet conditions. Everything from the screw-down crown to the solid case back contributes to its resilience.