Photo: eBay listing (seller: timewithpop)
The original Triple Sensor — the ABC watch before the category existed, at $75.
Verdict
| What it is | Casio Pro Trek PRG-40 — original Triple Sensor (altimeter, barometer, compass), WR 100M |
| Price | Buy It Now $75.00 or Best Offer + $12.70 shipping, spotted Sat Nov 7, 2026 |
| Where | eBay item 227590544803, seller timewithpop |
| The angle | The other live PRG-40 lists at $149 — this one, stated as running on new batteries, is half that |
| Verdict | Seller states new batteries and running well, with crystal scratches disclosed. At $75 against a $149 comparable, the gap checks out. |
What it is
Casio's PRG-40 was the ABC watch before the category existed: altimeter, barometer and compass from the original Triple Sensor, in a WR 100M case built to be worn outdoors and knocked around. It is the ancestor of every Pro Trek that followed, and the form factor — big, legible, sensor-forward — has not really changed since.
The seller, timewithpop, writes: "Pre-owned — Good"; "New Batteries and Running well... surface scratches on crystal but no major cracks. Selling as is." No returns. That wording ran in the Instagram post as written. This was the day's third draft: Matthew passed on a Bertucci and a Garmin alternate and chose the PRG-40 — the value check is in the price record: another live PRG-40 at $149 Buy It Now, and the US Pathfinder PAG-40 equivalent at $109.99.
Why it matters
The eBay Pick bar is a checked value gap, or no pick. Here the gap is same-model and live: $75 against $149 for the other PRG-40 on the same marketplace, for a watch whose job — altitude, pressure, heading — is exactly the urban-explorer tool brief, from the era when Casio invented it. Sensor watches have become smartwatches; the PRG-40 is the dedicated-instrument version, and it still does the job on batteries the seller says are new.
Specs
| Brand | Casio |
| Model | Pro Trek PRG-40, original Triple Sensor (per listing) |
| Sensors | Altimeter, barometer, compass (per listing) |
| Water resistance | WR 100M (per listing) |
| Condition | "Pre-owned — Good" — surface scratches on crystal, no major cracks (seller's wording) |
| Running condition | "New Batteries and Running well" (seller's wording); selling as is |
| Returns | No returns (per listing) |
| Service history beyond batteries | Not stated |
What to check before buying
- No returns, "as is" — even with a running statement. The seller's battery and running wording is quoted, not verified by us. Ask about sensor calibration before buying.
- Crystal scratches are disclosed. "Surface scratches... no major cracks" — the listing photos are the measure of how much that matters on a sensor display.
- Best Offer is live. $75.00 or Best Offer, plus $12.70 shipping. The comparable at $149 is the anchor for any offer.
- Triple Sensor calibration drifts. Altimeter and compass need setup against known references — true of every PRG-40, not a fault of this one.
Price record
| Spotted | Sat Nov 7, 2026, 3:33 PM PT — Buy It Now $75.00 or Best Offer + $12.70 shipping |
| Format | Buy It Now or Best Offer (eBay item 227590544803) |
| Also spotted | Garmin Foretrex 401, tested working, $95.00 or Best Offer, free shipping; Marathon SERE compass, new, $89.96 (per the day's caption) |
Want one?
- In the shop: browse current stock — one-off pieces, and they turn over fast.
- Hunting one? Join the Want List — tell us the maker and the budget; pieces like this surface in our trawl most weeks.
- This one: at the source — See it at eBay — item 227590544803. Not our listing. See Disclosure.
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- Casio G-Shock MR-G MRG-1 on eBay — the first MR-G, at $95
- RZE UTD-8080-ST — a titanium digital, at $399
- Bulova Oceanographer on ShopGoodwill — a dual-day diver behind a "35 Jewels" listing title
Spotted, not sold by us — this piece lives at an eBay listing by a third-party seller. Prices are a snapshot from when we spotted it. Disclosure
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Shop the pick
Casio Pro Trek PRG-40 Triple Sensor
$75.00 or Best Offer + $12.70 shipping — eBay listing, spotted Sat Nov 7, 2026
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