Very interesting!!! Did it come with a decent strap? I'm guessing that's not the OEM strap on there.Old School domed thick Acrylic any scratches buff out with Polywatch in seconds. The case back and crystal work on the "Super Compressor" action of the deeper you dive, the water pressure pushed down and the case back and crystal sealing it even tighter. When you unscrew the case back you are only unscrewing the sealing ring, the rest of case back doesn't rotate off the back like normal watches. When the case back is finally pulled off you will see a sealing gasket about 20 times a thick at a normal watch, this gasket isn't subjected to shredding like a normal case back is when taking the case back off and on. The design for this watch was really exceptional, they didn't want to copy any of the Swiss models so as to avoid patent problems, these watches were designed from the ground up.
Nice watch, I see it's for sale on eBay.