Introducing
Momentum’s revival of the Chronosport dive watch from Magnum, P.I. now comes in a 38mm case, keeping its 300m rating and Swiss quartz, with pre-orders from EUR 293.
Momentum’s Sea Quartz 30 is a 42mm dive watch, and the brand says it rebuilt it from the original Chronosport case design. The new Sea Quartz 30 Heritage squeezes the same black dial, orange minute hand, day-date display, broad cushion case and protected crown into 38mm.
So the Heritage 38 is a smaller take on the Magnum, P.I. watch rather than a return to its original size. Momentum says it was made for customers who liked the 42mm but wanted something better suited to slimmer wrists. We haven’t handled it yet, so everything below about size and proportion comes from Momentum’s figures and official images.
What changes at 38mm
On paper, the Heritage 38 is 38mm across, 11.7mm thick and 43mm lug-to-lug, with an 18mm lug width. The 42mm model is listed at 47mm lug-to-lug with 20mm lugs, so 4mm comes off both the diameter and the length. With a cushion case, lug-to-lug is usually the figure that decides whether a watch fits a smaller wrist, and 43mm suits far more of them than 47mm.
Thickness goes the other way. Momentum lists the 42mm at 11.3mm, which makes the Heritage 0.4mm thicker on paper. That’s a small difference, but with less diameter around it, the 38mm case is proportionally the chunkier of the two.
The narrower lugs matter if you already own the 42mm: its 20mm straps won’t fit. Momentum sells its straps in 18mm too, including the OceanFlex rubber that comes in the bundle.
Chronosport, 1977 and Thomas Magnum
Momentum is the brand of St. Moritz Watch Corp. in Vancouver, and its founder and his family previously owned Chronosport. Chronosport launched the Sea Quartz 30 in 1977, and Momentum calls it the first analogue quartz dive watch on the general market. Tom Selleck then wore one as Thomas Magnum for the first three seasons of Magnum, P.I., which began on CBS in 1980.
Swiss quartz, as in 1977
There’s no automatic option. Inside is a Swiss Made quartz day-date movement listed as the 507. The 42mm watch’s spec sheet names a Ronda R507; the Heritage page gives the number without naming a maker. Quartz is also the faithful choice here, since the 1977 original was sold as a quartz dive watch.
The case is 316L stainless steel, the sapphire crystal has anti-reflective coating on the inside, and the crown screws down. Water resistance is 300m and the dive bezel rotates. Momentum lists C3 Super-LumiNova, the sapphire and the 300m rating as its upgrades over the original.
What EUR 340 buys
Momentum’s EU store lists the Heritage 38 on its steel bracelet at EUR 293, against EUR 383 for the 42mm Sea Quartz 30 on steel. The bundle costs EUR 340 and adds a black OceanFlex rubber strap and a Momentum travel case. The 18mm OceanFlex strap alone is EUR 41 on the same store, so the case effectively costs EUR 6.
Both versions are pre-order only. Momentum says quantities are limited and expects to deliver in early November.
Thomas Magnum had the wrists (and the Ferrari) for the big one. The 38mm is for everyone else.
Specifications – Momentum Sea Quartz 30 Heritage 38
Case: 316L stainless steel; 38mm diameter, 11.7mm thick, 43mm lug-to-lug, 18mm lug width; screw-down, protected crown
Crystal: Sapphire, anti-reflective coating on the inside
Caseback: With sailboat emblem
Water resistance: 300m
Bezel: Rotating dive bezel
Dial: Black; luminous markers; orange minute hand; day-date display; C3 Super-LumiNova
Movement: Swiss Made quartz, 507, day-date
Strap/bracelet: Stainless steel bracelet; the bundle adds a black OceanFlex rubber strap and a Momentum travel case
Price: EUR 293 (steel bracelet); EUR 340 (bundle). Momentum EU online store, 8 October 2026
Availability: Pre-order, limited quantities; delivery expected early November 2026
