Casio AMW-320 - Sylvester Stallone - Samaritan
The watch actually plays an important role, key plot point, in the movie. The boy Sam Cleary, played by Javon Walton, has his father's broken watch, which Sylvester Stallone offers to fix.
The 1980s watch in the film has a black dial and a black bezel, with what looks like gold colored hands and markings on the bezel, possibly the AMW-320D model variation.
The same model is available in different colors, including one with silver markings and hands. Another famous variation of this model is the Casio AMW-320D-9EV with gold dial, which is worn by Arnold Schwarzenegger in Kindergarten Cop (1990).
In the film the watch has a green Nato or Zulu strap.
Find this vintage Casio AMW-320 on eBay.
With thanks to Scott for the ID