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Model comparison

Choose two or three models: movements, dimensions, functions and prices from our reviews.

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Prices come from the reviews in their original currency and market. Article dates are shown below.
SpecificationSeikoProspex Alpinist
ReferenceSPB121J1
WindingAutomatic winding
Calibre6R35
Diameter39.5 mm
Fit dimensionsDimensions: 39.5 × 13.2 mm; 46.4 mm lug to lug
Power reserveApproximately 70 hours
Case materialNot stated in the review
FunctionsNot stated in the review
CrystalSapphire with date magnifier
Water resistance20 bar
Price and marketPrice checked: $725, official US market
How to read dimensions and compare fit

Specifications help narrow your choices, but cannot replace trying a watch on. A dimension missing from a review is unknown, not zero.

Reference
The code identifying a specific watch variant. Dial, case material and other details can differ within one model family, so check the exact reference.
Diameter
The measurement across the case. Diameter alone does not describe fit: case length, lug shape, thickness and strap or bracelet construction also matter.
Thickness
The height of a watch affects how it fits under a cuff. Check whether the stated measurement includes a raised crystal, as measurement methods can differ.
Lug-to-lug versus lug width
Lug-to-lug is the length from the tips of the lugs on one side to those on the opposite side. Lug width is the gap where the strap attaches. These are different dimensions; projecting bracelet end links can add to the span on your wrist.
Water resistance
Metres, bar and ATM describe test pressure, not a permitted diving depth. Follow the specific model’s instructions for swimming and diving; seal condition and strap material also matter.

A practical starting point: compare diameter, thickness and lug-to-lug with a watch you already find comfortable. Even identical dimensions do not guarantee identical fit.

Seiko · Prospex Alpinist

Strengths

The Alpinist succeeds as a watch with a face of its own: a compact diameter, richly detailed dial and useful reserve.

Things to consider

The 6R35 tolerance is −15/+25 seconds per day. A 20-bar case rating does not turn the supplied leather strap into a water accessory.