Casio GMW-15 – Restoration

The Casio GMW-15 “Moon Graph” made its debut in 1986, and even today it feels futuristic. With its moon phase tracker and a calendar running up to 2029, it stood out as one of Casio’s most advanced digital watches of the 80s. For me, it’s not just another vintage pickup — it’s the oldest watch in my collection and a true milestone in Casio’s design history.

When I first saw this piece online, it wasn’t in great shape. The glass and case were scratched, the buttons were sticky, the strap was damaged and non-original, and worst of all, the sound was dead. Many collectors might have left it as a parts watch, but I knew it was worth saving.

This post covers how I restored the GMW-15 step by step: cleaning and polishing the case, repairing the buttons, fixing the buzzer, and fitting a strap that matches its original look. The end result is a fully functional Moon Graph, ready to track lunar cycles for decades to come. 🌙⌚

the watch’s initial condition

When the Casio GMW-15 arrived, it showed every sign of long-term wear. The acrylic glass and plastic case were scratched all over, making the display look cloudy. The buttons were sticky and difficult to press, which is a common issue when dirt and oxidation build up over the years.

The watch also came with a damaged non-original strap. Not only did it look wrong, but it made the watch uncomfortable to wear. On top of that, the sound wasn’t working at all — the beeper was silent because the small spring connecting the module to the piezo buzzer was missing.

It was far from collector-ready. Still, underneath the flaws, this was a rare 1986 Moon Graph with unique features worth bringing back.

👉 Collector’s note: Moon Graph models don’t show up often, and many surviving examples suffer from scratched crystals, failed buzzers, or broken screens. Finding one complete and restorable is already a small victory.

How did I restore the Casio GMW-15?

Step 1: Sanding and polishing the glass and case

The glass had deep scratches, so I started with wet sanding. I used grits from 400 up to 2200, carefully reducing the marks layer by layer. After that, I switched to a polishing machine to bring back full clarity and shine. The case got the same treatment, which removed years of scuffs and gave it a smooth finish again.

Step 2: Repairing the buttons

Next, I worked on the sticky buttons. I filed and polished their surfaces, then cleaned the contacts. After this, they clicked properly again and no longer got stuck.

Step 3: Restoring the sound

The beeper was silent because the spring that connects the module to the piezo buzzer was missing. I added a replacement spring, and the sound came back instantly. Hearing that familiar Casio beep after years of silence was a highlight of the whole project. 🔧

Step 4: Replacing the strap

The non-original strap was unusable. I fitted a new strap designed to match the model’s style, which not only improved the look but also made the watch comfortable and wearable again.

Final result

After the work was done, the Casio GMW-15 Moon Graph looked and felt like a different watch. The glass was polished clear, the case regained its shine, and the buttons clicked smoothly without sticking. Adding the missing buzzer spring brought back the signature Casio beep, and the new strap gave it the right vintage look on the wrist. All functions — from the moon phase tracker to the calendar stretching to 2029 — are now working perfectly.

For me, this restoration was special. It saved the oldest watch in my collection and brought back a rare piece of Casio’s experimental era. 🌙⌚

Now I’m curious: do you have a Moon Graph in your collection, or maybe another vintage Casio with lunar features? Have you ever restored one yourself, or are you planning to? Share your stories, tips, or photos in the comments — I’d love to see how other collectors have brought theirs back to life.