There existed watches with the same digits, features and buttons before that, but they were in steel. 1989 is about when Casio transitioned from metal to resin.
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.
The F-91W is such a fun watch. Super functional, you're not scared of damaging it, because A) You can't and B) it's like $25.
The backlight is my absolute favorit feature. It's completely pointless. It can barely light up the hours, and only the left most digit and Casio never bothered to fix it. Absolutely delightful.
Casio is still super hit or miss with backlights. I have a Casio Lineage LCW-M100TSE-1AER and the light is even less useful for its display. Otherwise it's very nearly a perfect watch for me.
I always bump the 24H button on the F-91W, I'm not entirely sure why Casio felt like you should be able to switch between 12h and 24h at the push of a button. My assumption is that most people stick to either of the two formats, jumping between them seems like a edge case.
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.