Professional helium valve on 9:00 oclock, in order to be able to lead during external pressure reduction (e.g. emerging) the accumulating helium fast enough from the clock.

Date at 3:00
central second hand
adjustable 60 min. Diverbezel only anti clockwise
casesize 40mm; thick 13mm; all stainless steel
Screwed Crown; diameter 7mm
20 atm water resistant
high quality SWISS-RONDA Cal. 515.24H quartz movement
hardened mineral glas with date-Lens
screwed bottom
illumious hands and indexes
high quality Stainless steel strap with protecting clasp (max. circumference 220mm)
delivery with certificate
24 months warranty

Comment:

The helium valve is especially for occupation diver interesting, who are held also in air environment on pressure. Helium atoms are so little that they can penetrate through sealings into the clock and can construct an interior pressure. This is further not tragically - if all helium atoms could leave in outside pressure reduction quickly enough the clock. For this case we add this special valve, which lets the helium-atoms again outward, otherwise it would come to an explosion of the clock.