Owned that one since new in '91. Been telling everyone '92 but found the receipt the other day.
Only changed the original battery in Jan 2013. It was lost for a year in my garden and had lost a few seconds when I was found the next year. It's been on my wrist while I was a mechanic and welding. I dive with it all the time. It's been in oil, paint thinners and other horrible substances. Never skipped a beat.
As for scratch resistant crystal? I decided to remove a couple of small scratches it has got over the 20+ years. I got my kit that I do the 6139-6000 Hardex crystals with. I started with the 400 grit disc on my grinder and happily ground away for 10 minutes then I notice the scratches were not going! I wiped the dial and it's unmarked by the grinding disc! These are true Sappire crystals and can only be polished with diamond powder based polish I am guessing.
To show a customer how strong it is (been run over by heavy vehicles on purpose too) I kept throwing it at a brick wall the other day. He laughed his head off and couldn't believe it just kept going. That's a 23 year old watch I am chucking at full strength at a brick wall and it just keeps going... These things are harder than Chuck Norris with his balls in a vice! Amazing bits of kit.... the G-Shock not Chucks balls.