Certina DS-2 Super PH500M

Case Diameter: 43 mm
Case Height: 17 mm
Case length: 47.5 mm
Lug Width: 19.5 mm
Movement: Certina 25-651, 27j, 19,800 bph,
42 hr power reserve
Case material: Stainless steel
Crown : Screw down
Bezel: Bi-directional, indexed w/ 120 clicks
Water resistance: 500 meters
Vintage: late '60s.
Shown for comparison with a full sized Rolex Submariner you can see
how thick the case of the DS-2 is.

This is a very thoughtfully designed watch. The 5mm thick acrylic
crystal is sealed against the case with an o-ring, and secured by a
threaded retaining ring. The retaining ring is easily removed, allowing
easy replacement and servicing of the crystal, o-ring and bezel without
the need of a watchmaker or watchmaker's tools. The bezel on this
watch has one of the most precise actions I have seen on any watch,
vintage or modern. Drilled case lugs are a nice touch and make strap
changes fast and easy.

Today Certina is just another brand name in the SWATCH GROUP,
but back in the day Certina built their reputation with some very serious
dive hardware.