Swift (Asus Zenwatch 3) is a fashion-oriented watch with limited hardware but a very unique design.
Swift is a medium-size round watch with an OLED display and a steel case. The side of the watch has 3 buttons, none of which act as a rotating input. The top and bottom of the watch extend out to the strap with a pair of unique-looking metal panels. While the straps are 20mm wide, the ends that mate into the case of the watch are only 14mm. While the straps are theoretically replaceable, you'll need to either buy straps specifically intended for this model or modify some of your own. Bluetooth currently doesn't work.
The back is held on with screws and a rubber seal, so opening the watch will not compromise water resistance, and there aren't even any ribbon cables to manage once the back comes off because everything is secured with pogo pins. Battery replacements are available.
Miscellaneous hardware docs
The central key is the power key. The top and bottom extra keys map to volume up and down respectively.
Manually getting to fastboot
During the first seconds of the boot process, swipe diagonally across the screen. Starting from the top/left outer edge of the screen to the bottom/right.