Seiko just updated one of the better-kept secrets in its Prospex line. The 1968 Heritage Diver's GMT gets two new references, HBC001 in green and HBC002 in black, replacing the SPB381 and SPB383 that launched back in 2023. Nothing about the design changed. What's underneath the caseback did.
What's actually new
The spec sheet for the original was already strong for the money: a 42mm case with mirror-polished sides, a ceramic bezel insert, 200m water resistance, an AR-coated sapphire crystal, and the in-house Calibre 6R54 automatic GMT movement with a 3-day power reserve. All of that carries over untouched.
Two things changed. Water resistance jumped from 200m to 300m, without adding a millimeter to the case's 12.9mm thickness. And the clasp swapped from a diver's extension, useful underwater but clumsy for daily wear, to a push-button microadjustable clasp with 15mm of travel across six 2.5mm increments.
That clasp is the update that actually matters day to day. A diver's extension is built for wetsuits, not wrist swelling from a hot commute or a flight. Six adjustment points means the watch can be fitted properly instead of one notch too loose or too tight.
Price and availability
The new references cost $1,700, up from the original $1,500. That $200 matches what Seiko already charges for other 1968 Heritage Diver's GMT editions carrying the same clasp and water resistance bump, like the SPB534 and SPB519, so this isn't a new premium, just the standard spec now applied across the line. Both generations are currently listed on Seiko's site at the same time, though it's unclear how long the older SPB381 and SPB383 will stay available at the lower price.
If the GMT complication and heritage dive case are what you're after and you don't need the newest clasp, the Seiko Prospex 1965 Heritage Diver "Save the Ocean" SPB545J1 is in stock now and sits in the same family of reissued Seiko dive cases.
