Collector Notes · September 28, 2026
Casio F-91W-1: Why the Black Resin Digital Still Matters
A buyer-focused guide to Casio’s black F-91W-1: size, functions, limits and what to check before buying.
A buyer’s guide to Casio’s black resin F-91W-1 configuration. Facts and image rights checked September 28, 2026.
The Casio F-91W-1 is a useful reminder that a watch need not be complicated to earn a place in a collection. Casio introduced the F-91W in 1989. The current black resin configuration keeps the familiar compact case, legible digital display, alarm, stopwatch and simple LED light. For a buyer, its appeal is specific: low weight, straightforward operation and the ability to see the time at a glance.
What the reference offers
Casio lists the F-91W-1 at 38.2 × 35.2 × 8.5 mm and 21 g. Its case, bezel, band and crystal are resin. On a wrist, those figures describe a slim, light watch rather than a substantial sports case. The design is practical, with a broad display, blue framing around the dial and red accents on the black face.
Daily functions
The watch has a 1/100-second stopwatch that measures up to 59 minutes, 59.99 seconds, a daily alarm, an hourly time signal, a 12/24-hour display and an LED light. Casio rates accuracy at ±30 seconds per month and battery life at approximately seven years on a CR2016. That estimate is a specification, not a promise for every pattern of use.
Where it has limits
Casio labels this model “Water Resistant” without publishing a depth rating on the referenced product page. Treat that as protection against routine splashes, not an invitation to swim or shower with it. The LED is a simple utility light, not a fully illuminated display. The auto-calendar is set for 28 days in February, so the date needs a manual correction in a leap year.
What to check before buying
Check the exact reference and the black resin, blue-and-red dial configuration against Casio’s product photography. On a used example, inspect the case edges, buttons, strap, buckle, display and back screws. Test the alarm, stopwatch, light and mode changes. A fresh battery does not cure worn buttons or damaged sealing. If water exposure matters, ask a competent watchmaker to inspect and test the case after any battery change.
The Rallo verdict
The F-91W-1 makes sense if you want a light, compact digital watch with a small set of genuinely useful functions. It is less suitable if you want a bright modern backlight, a metal case, or a stated swim rating. Buy the reference for what it does well: dependable everyday timekeeping in an uncomplicated package.
Sources and photograph credits
Specifications and model history: Casio F-91W-1 product page, checked September 28, 2026.
Casio F-91W history, checked September 28, 2026.
All five photographs: Multicherry, Wikimedia Commons, licensed CC BY-SA 4.0 for reuse with attribution. Images are presented without watch retouching. Source files:
side: https://commons.wikimedia.org/wiki/File:Casio_F-91W_watch_(2023)_(right-hand_side_closeup).jpg
light: https://commons.wikimedia.org/wiki/File:Casio_F-91W_watch_(2023)_(LED_light).jpg
back: https://commons.wikimedia.org/wiki/File:Casio_F-91W_watch_(2023)_(rear_view_-_full_length).jpg
License terms: Creative Commons Attribution-ShareAlike 4.0 International.