Seiko Alpinist SPB121 vs Hamilton Khaki Field Titanium Auto

Both are field watches in the upper tier. In short: the Seiko Alpinist SPB121 takes more water (200m) — both are fine for swimming, but it has more margin if you dive. The Seiko Alpinist SPB121 is automatic, 200m water resistance, 39.5mm, sapphire crystal; the Hamilton Khaki Field Titanium Auto is automatic, 100m water resistance, 42mm, sapphire crystal.

Last verified 2026-06-27 · specs from manufacturer data · tier = price band, confirm the live price at the retailer

Spec	Seiko Alpinist SPB121	Hamilton Khaki Field Titanium Auto
Movement	Automatic	Automatic
Water resistance	200m	100m
Case size	39.5mm	42mm
Crystal	sapphire	sapphire
Style	Field / explorer	Field / explorer
Price tier	Upper	Upper

Which should you buy?

The Seiko Alpinist SPB121 takes more water (200m) — both are fine for swimming, but it has more margin if you dive
The Seiko Alpinist SPB121 wears 39.5mm vs the Hamilton Khaki Field Titanium Auto's 42mm — choose by wrist size

Where to buy

Seiko Alpinist SPB121See price on AmazonCheck price

Hamilton Khaki Field Titanium AutoSee price on AmazonCheck price

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FAQ

What's the difference between the Seiko Alpinist SPB121 and the Hamilton Khaki Field Titanium Auto?
Both are field watches in the upper tier. The Seiko Alpinist SPB121 is automatic, 200m water resistance, 39.5mm, sapphire crystal; the Hamilton Khaki Field Titanium Auto is automatic, 100m water resistance, 42mm, sapphire crystal.

Which has better water resistance, the Seiko Alpinist SPB121 or the Hamilton Khaki Field Titanium Auto?
The Seiko Alpinist SPB121, rated 200m, versus 100m on the other. Pick 100m or higher for swimming and 200m+ for diving.

Which is better value, the Seiko Alpinist SPB121 or the Hamilton Khaki Field Titanium Auto?
Both sit in the upper tier, so it comes down to movement, water resistance and case size — see the spec table above.

Citing these specs? Go ahead — manufacturer data, last verified 2026-06-27. Copy a ready-made reference:

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