Casio BP-100 – Restoration

How did I find this watch?

The Casio BP-100 is one of the boldest experiments from Casio’s golden era. Released in the late 80s, it came with a built-in pulse and blood pressure monitor—a feature so unusual that it felt like science fiction at the time. While most digital watches focused on databanks, calculators, or moon graphs, Casio tried to turn your wrist into a tiny medical lab 😅.

I came across this BP-100 on eBay in the U.S. and decided to bring it over to Poland. For me, finding one is always exciting. These models appear often, but especially not as complete sets. And every time you open the box of a vintage Casio, you’re stepping into a small piece of history.

What was the initial condition of the watch?

When I first inspected the Casio BP-100, here’s what I found:

• Display: completely blank, no response from the module.
• Strap: original resin strap present but stiff and uncomfortable after decades of aging.
• Case: multiple scratches across the resin body and bezel from regular wear.
• Crystal: surface scratches and dull finish that hid the clarity of the LCD.
• Back plate: no signs of tampering, screw heads sharp and untouched.
• Battery: original Japanese NOS (New Old Stock) cell still inside, completely drained.
• Missing parts: none, which was a relief. Both springs (buzzer and sensor contact) were present.

Overall, the watch looked rough but complete. From a restoration perspective, that’s the best starting point you can ask for 👍. No previous DIY attempts, no water damage, and no missing hardware—just a tired survivor waiting for some attention.

How did I restore the Casio BP-100?

With the watch inspected, I moved step by step through the restoration process.

1. Battery replacement

The first task was obvious. I removed the old Japanese NOS (New Old Stock) cell and installed a fresh battery. The module came back to life instantly, which was a great sign. Always replace carefully here, since the BP-100 uses two contact springs: one for the buzzer and one for the sensor. Losing them is a common headache among collectors.

2. Case refinishing

Next, I worked on the resin case. I filed down deeper scratches using fine sandpaper (starting at around 1000 grit and moving up). After that, I smoothed the surface until it had an even, clean finish.

3. Restoring the text

The white printing on the bezel had faded. To refresh it, I used white nail polish. I applied a thin layer into the recessed letters, let it dry, then carefully wiped away the excess with acetone on a cotton swab. This brought the lettering back to sharp contrast.

4. Crystal polishing

The acrylic crystal had a dull, scratched look. I started with sandpaper to remove the deeper marks, then switched to a polishing felt wheel on a small grinder. A final touch with Polywatch gave it clarity again. Doing this by hand first helps control the finish, while the machine makes the surface shine.

5. Strap replacement

The original BP-100 strap is rare and very expensive on eBay. Instead, I fitted a strap from the Casio SDB-500, which matches well and keeps the watch wearable. For me, usability comes before chasing a NOS strap that costs more than the watch itself 😅.

What challenges came up during the restoration?

No restoration ever goes perfectly. The BP-100 had a few moments that needed extra attention.

Strap problem

The original BP-100 strap is notoriously rare and expensive on eBay. Some listings ask more than the watch itself, which feels a bit crazy. My solution was simple: I swapped in a Casio SDB-500 strap. It fits well, keeps the watch wearable, and looks close enough to the original design. For me, usability matters more than chasing overpriced parts 😅.

Keeping the sensor functional

The blood pressure sensor is one of the quirkiest parts of this model. At first, I had trouble getting consistent readings. The fix was all about finger placement. Once I adjusted how I pressed the contacts, the sensor worked much better. A good reminder that Casio’s instructions weren’t just for decoration.

Spring issues

Inside the BP-100, there are two small contact springs: one for the buzzer and one for the sensor. They are tiny and very easy to lose during a battery swap. I’ve lost a few over the years. A handy trick: you can strip a spring from an old lug bar or spring bar, cut it to size, and use it as a replacement. It works perfectly and keeps the watch running.

How did the Casio BP-100 turn out after restoration?

After working through the restoration steps, the BP-100 came back to life both visually and functionally.

• Module: fully operational. The pulse and blood pressure functions worked consistently once I dialed in proper finger placement. For a watch from the late 80s, that still feels futuristic ⌚.
• Case: scratches filed down, surfaces smooth again. The resin regained a uniform finish.
• Text: bezel lettering crisp and sharp after the nail polish refresh.
• Crystal: polished clear, letting the LCD shine without haze or distracting marks.
• Strap: fitted with the Casio SDB-500 strap, which makes the watch comfortable and wearable without hunting for an overpriced NOS band.
• Set: this example came as a complete package, with box, cassette with instructions, and original papers. For collectors, that’s a big win.

Seeing it powered up and looking clean was satisfying. There’s something special about reviving a model that sat untouched for decades. The BP-100 may not be the toughest Casio ever made, but it represents one of the brand’s most ambitious experiments. And that makes it a highlight in my collection 👍.

What do you think?

That was my journey with the Casio BP-100. For me, it’s one of the most unusual Casio experiments, and bringing this one back to life was worth every step of the process 🛠️.

I’d love to hear from you:

• Have you ever owned or restored a BP-100?
• Did you manage to get the blood pressure sensor working consistently?
• Do you have any tips or stories about restoring other databank-style Casios?

Drop your thoughts, memories, or restoration stories in the comments. Sharing these little victories keeps the vintage Casio community alive 👍.