The CasiOak is a FULL METAL 2100 Series GM-B2100D-1A Stainless Steel G-SHOCK, not even a year old, worn less than 10 times.
size: 49.8 × 44.4 × 12.8 mm (44mm case)
Shock Resistant, Water Resistance up to 200-meters,
Bluetooth: Connects to a smartphone and automatically adjusts the time. Power supply and battery life by Tough Solar (solar powered) Everything that was initially bought comes with it. I originally paid $850 for it new, so getting it for $200 off isn't a bad deal.
More info:
https://www.casio.com/intl/watches/gshock/product.GM-B2100D-1A/
