I was really surprised to find out that the F-91W was first released in 1989. I had assumed it was even older than that! I wasn't too surprised to see their blurb leave out it's other (alleged!) known use https://en.wikipedia.org/wiki/Casio_F-91W#Usage_in_terrorism
The metal watches were succeeded by the A158W, which is chrome-plated resin on the outside, same electronics module as the F-91W on the inside, and likewise is still in production.
After the resin case of my A158W eventually broke, I got a vintage W-34 with a broken movement and put the A158W's module inside. (It will get a SensorWatch PCB once I am done with my firmware mods)
Steel replacement cases for a F-91W are now also available on Aliexpress, so you don't have to hunt down a vintage watch if you want real steel.