I love the F91W. This is a genuine Casio - which you don't always get on other websites. The watch is so light, it has an alarm and stopwatch. The only issue with this watch is that the straps break after a while. I typically break a strap every 2 years (wearing every day). Annoyingly, replacement straps are the same cost (or more) as a new watch - so I just buy a new watch every couple of years. Non-genuine replacement straps tend to be thick and bulky and also don't look as clean. Amazon - if you're reading this - please stock some genuine Casio replacement straps!
Some of the other reviews noted that the strap was too small, but mine was totally fine, with about 6 notches to spare. Appears to be a standard F-91W. I've had about three of these now and they are super reliable, usually keeping the time within 1 sec per day. The only problem is that the strap will wear out after about a year, if worn every day, and it costs about the same as the watch to replace, which is a shame, because the watch lasts about 5 years before a battery replacement.
I love it! Such an iconic watch. Keeps time well, has date and day features, daily and hourly alarms and a neat stopwatch. Now, in terms of authenticity; I've done the usual checks and I believe it to be authentic. The numbers are aligned, has the CASio Easter egg and the greenish screen. These ones are made in Japan as opposed to China. You can't get authentic ones in Australia this cheap! The price is great.
Fantastic and timeless (ha). This watch is a classic and a fantastic daily driver. Does what it needs to, tell the time. The light is your standard single LED affair, nothing fancy but that's the point. The design hasn't changed in nearly 30 years for a reason!