Casio PRL-20 ‘Ley’
The Pro Trek I Didn't Know I'd Bought
Sometimes the Watch Finds You
There are watches I've spent weeks or months looking for.
And then there's my Casio PRL-20 ‘Ley’.
I'd already been looking at one on eBay and had actually started bidding on it. It was a model I wanted for the collection, so I was keeping an eye out for the right example.
Then a completely unrelated bundle of watches arrived.
And sitting amongst them was a PRL-20.
It hadn't even been shown in the seller's photographs.
I was bidding on one elsewhere while another one was already on its way to me without me even knowing it.
You couldn't plan it.
And Then There Were Two
The surprise didn't stop there.
Alongside the Pro Trek was another watch that, at first glance, looked virtually identical.
Turn it over, however, and the caseback carried the Pathfinder name and the reference PAL-20.
So an unadvertised PRL-20 Ley had appeared in the bundle, accompanied by its Pathfinder relative.
There was just one problem.
Neither of them worked.
Two Dead Watches, One Working Pro Trek
At that point the sensible option might have been to put them aside until I could source whatever parts each one needed.
Naturally, I didn't do that.
I started investigating both watches and discovered that between them I had enough usable parts to get one running.
So the two non-runners effectively became donors for each other.
A bit of cleaning, testing, swapping and what can only really be described as MacGyvering later, and the PRL-20 was alive again.
That was the important part.
The Pro Trek I'd been actively looking for was now sitting in my collection and working.
The Pathfinder Wasn't Finished Either
For a while, the PAL-20 had done its job as part of the rescue operation.
But I wasn't particularly happy leaving another interesting old Casio dead if there was a chance of saving it.
So I kept working on the Pathfinder too.
Eventually, that one came back to life as well.
The end result is considerably better than I could have expected when I opened that bundle: I now have my working PRL-20 Ley, the Pathfinder is running too, and I've even ended up with a spare working module.
Not bad for two watches that initially appeared to be dead.
An Early Pro Trek With Proper Outdoor Functions
The PRL-20 comes from an interesting period in Casio's outdoor-watch history.
This was before the enormous modern Pro Trek cases and before GPS, Bluetooth and smartphone connectivity entered the picture.
The idea was much simpler: give somebody heading outdoors useful environmental information directly on the wrist.
Surviving PRL-20 Ley references describe a Twin Sensor arrangement providing altimeter, barometer and thermometer functions, together with a barometric-pressure trend graph and the ability to record and recall altitude data.
That's proper Pro Trek territory.
Even now, those are genuinely useful outdoor functions rather than features included simply to make a specification sheet longer.
The Display
One thing I particularly like about these older sensor Casios is how much information they manage to present without relying on a huge modern screen.
The PRL-20 has that unmistakable 1990s Casio look.
There's plenty happening on the LCD, including the environmental data and graphical information, but it still feels like a watch rather than a small computer strapped to the wrist.
For me, that's a big part of the appeal.
It's old technology now.
But it's clever old technology.
Barometer and Weather Trend
The barometer is particularly useful because the watch isn't limited to giving you a single pressure reading.
The display can show a barometric-pressure trend graph, allowing changes over time to be viewed at a glance.
That means the watch isn't simply telling you what the atmospheric pressure is at that exact moment.
It's giving you information that can help indicate how conditions are changing.
For a watch from the 1990s, that's still impressive.
Altimeter
The altimeter is another major part of the PRL-20's identity.
The watch can estimate altitude using changes in atmospheric pressure and includes altitude recording and recall functions.
There is even an altitude alarm, allowing a target altitude to be set.
As with any barometric altimeter, readings depend on atmospheric conditions and calibration, but that's part of understanding how this type of sensor works rather than a fault with the watch.
This was designed as a genuine outdoor tool.
Thermometer
Then there's the thermometer.
As with most wrist-mounted temperature sensors, body heat can influence the reading while the watch is being worn, so the most meaningful ambient-temperature readings are obtained after allowing the watch to acclimatise away from the wrist.
Again, that's simply the nature of putting an environmental sensor in something you're wearing against warm skin.
The important thing is that Casio managed to combine all of these functions into a wearable package decades ago.
Pro Trek and Pathfinder
Having the PRL-20 and PAL-20 together makes this part of the collection particularly interesting.
Casio used both Pro Trek and Pathfinder branding in its outdoor/outgear ranges, and these two watches show just how closely related some of those models could be visually.
Mine initially looked almost identical until I turned them over and read the casebacks.
That's exactly the sort of little detail I enjoy with older Casios.
Two watches can appear virtually the same at first glance, then the references and module markings tell you there's more going on underneath.
A Note on the Module Numbers
There is conflicting information online about the exact module fitted to different PRL-20 variants.
Some surviving ‘Ley’ references identify module 1617, while a 1997 Casio service-manual listing explicitly associates QW-1675 with a PRL-20BV. The PAL-20 Pathfinder is also well documented with module 1675.
Because different PRL-20 variants appear to exist, I would rather record the module number from the caseback of my own watch than repeat an online specification that may belong to a different variant.
With vintage Casios, accuracy matters more than filling every line of a specification table.
The Pro Trek I Didn't Know I'd Bought
That's still the part of the story that makes me smile.
I wanted a PRL-20.
I was actively bidding on one.
And completely unknown to me, another example was already sitting inside a bundle I'd bought for other watches.
It wasn't photographed.
It wasn't advertised.
It was simply there when the parcel arrived.
Then it turned into a restoration project.
Then the Pathfinder joined in.
And somehow I ended up getting both watches running.
Sometimes you hunt for a particular watch.
Sometimes the bloody thing just turns up on your doorstep.
The Casio Collector Verdict
The Casio PRL-20 Ley is one of my favourite examples of pure luck turning into a restoration project.
I'd already decided I wanted one and was bidding on an example on eBay when an unrelated watch bundle arrived.
Hidden inside - and not even shown in the listing photographs - was a PRL-20.
Alongside it was an almost identical PAL-20 Pathfinder.
Neither worked.
By using parts from the two watches, cleaning and testing everything and doing a bit of watch-repair MacGyvering, I managed to build the PRL-20 back into a working watch.
And I was delighted with it.
The story could have ended there.
Instead, I later managed to get the Pathfinder running too, and I've now even got a spare working module, 2 straps and a case with one tiny part missing ….. damn.
The PRL-20 itself is exactly the sort of older Pro Trek I enjoy. It's packed with genuinely useful outdoor technology - altimeter, barometer, thermometer and environmental data - without being enormous or overloaded with modern connectivity.
Most importantly, it's a watch I already wanted before I accidentally bought one.
I went looking for a PRL-20.
Turns out one had already found me, and it looks amazing on the Nato Strap I had chosen for it.
Specifications
Model: Casio Pro Trek PRL-20 ‘Ley’
Era: 1997
Movement: Quartz digital
Display: LCD with graphical sensor information
Outdoor sensors: Twin Sensor
Altimeter: Yes
Barometer: Yes
Barometric pressure trend graph: Yes
Thermometer: Yes
Altitude record/recall: Yes
Altitude alarm: Yes
Stopwatch: Yes
Alarm: Yes
Backlight: Electro-Luminescent on documented variants
Water resistance: 100 metres on documented PRL-20/PAL-20 variants
Related model in my collection: Casio Pathfinder PAL-20
Condition when acquired: Non-running; received unexpectedly in a watch bundle
Restoration: Parts from the PRL-20 and PAL-20 were initially combined to return the PRL-20 to operation
Current status: PRL-20 running; PAL-20 subsequently restored and running
Module note: Online records conflict between PRL-20 variants; the caseback/module marking on the individual watch should be treated as definitive
Personal highlight: I was bidding on a PRL-20 elsewhere when this one unexpectedly arrived in a bundle that hadn't even pictured it.
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