Seiko Mod Chronographs — Two Limited ST1901 Mechanicals

A hand-winding mechanical chronograph caliber in production since the 1960s — one of the oldest and most reliable workhorse chronograph movements in existence. Official accuracy is rated -10 to +40 seconds per day; across 30 pieces we tested dial-up, ours ran between -1 and +8 seconds per day (not every piece will match that, but it shows how the batch was built).

Yes — each ST1901 model is limited and exclusive to 100 pieces. The LA2201A speedmaster-style chronograph and the LA2201B pulsograph are 100 pieces each.

A pulsograph — also called a doctor's watch — carries a pulsometer scale on the dial. Start the chronograph, count the marked number of heartbeats, and the seconds hand points to the pulse rate per minute. Ours pairs the scale with an enamel-white dial and the hand-wound ST1901 chronograph caliber.