I would need to look up the ISO standards but (too lazy) - I have found this on the Internet, instead.
Unlike most dive watches these days this watch has an acrylic rather than a mineral glass crystal. You wouldn’t imagine that a regular acrylic crystal would be strong enough to resist the pressure of scuba diving, particularly as this watch is rated to a depth of 200m…. and you’d be right!
A much more substantial crystal is needed in this case, an armed diver crystal, which is around 3 times thicker than a regular acrylic crystal............
I suppose cutting corners to keep the price of a watch competitive; "inferior" components are used - but - what is the point!?