Sporty chronographs often come with a compromise. If you want multiple subdials, a tachymeter, and motorsport-inspired styling, you frequently have to accept a fairly large watch. That can make an otherwise practical chronograph less appealing if you prefer a case that stays below 40mm.
The Casio Edifice EFS-S660 PB-1A and EFS-S660D-1A address that problem with a 38.3mm-wide case while retaining solar power, chronograph functions, sapphire crystal, a date display, and 100-meter water resistance. The specifications are largely identical, so choosing between them mostly comes down to whether you want a lightweight resin band or a stainless-steel bracelet.
Price: ¥33,000 (About $210 USD)
Where to Buy: Casio
A smaller Edifice chronograph
Both EFS-S660 models measure 45.3 x 38.3 x 11.6mm, with that 38.3mm width being one of the most interesting numbers on the specification sheet. Casio itself emphasizes fitting the chronograph functions into a compact 38.3mm case.
For buyers, the 38.3mm measurement is what changes the equation. Anyone who finds larger sports chronographs excessive now has an Edifice option below 40mm without giving up the multi-dial layout.
That doesn’t automatically mean the watch will feel small or comfortable on every wrist. Fit depends on wrist size, case shape, and personal preference, so the dimensions are evidence of a compact case rather than evidence of comfort.
Solar power reduces battery maintenance
Both models use a solar charging system, with Casio specifying approximately five months of operation from a full charge until the hands stop if no additional charging occurs. There’s also a low-battery warning.
The useful part isn’t having another piece of solar technology on your wrist. It’s having fewer routine battery changes to think about. Light supplies energy to the watch during normal use, although actual charging naturally depends on how much light it receives.
Casio promotes stable solar power as one of the EFS-S660’s benefits. The evidence from the specification sheet is more specific: these are solar-powered watches rated to run for approximately five months from a full charge without further charging.
The chronograph measures to 1/20 second
The EFS-S660 has a 1/20-second stopwatch capable of measuring up to 59 minutes, 59.95 seconds, with elapsed-time, split-time, and first- and second-place measurement functions.
A tachymeter surrounds the dial, continuing the motorsport theme and allowing speed to be calculated over a known distance.
The formal specifications identify the centrally mounted hand as the stopwatch-seconds hand, while regular seconds are handled separately on a subdial. The other subdials display stopwatch 1/20 seconds and stopwatch minutes, and both models also include a date display.
Sapphire crystal and 100-meter water resistance
Both watches use sapphire crystal with an anti-reflective coating and carry a 100-meter water-resistance rating.
Those are useful specifications for an everyday sports watch. The sapphire crystal should appeal to buyers concerned about scratches and reflections, while the 100-meter rating gives the EFS-S660 more versatility around water than a watch designed only for occasional splashes.
Resin or stainless steel?
The biggest difference between the two models is the band and resulting weight.
The EFS-S660PB-1A uses a resin band and weighs 71 grams. It combines a stainless-steel case with gray ion plating, a black ion-plated bezel, and a red chronograph hand.
The EFS-S660D-1A uses a stainless-steel bracelet with a one-touch three-fold clasp and weighs 129 grams. Casio distinguishes this version visually with a blue chronograph hand.
That creates a substantial 58-gram difference, making weight one of the clearest reasons to choose between them. The resin version is the logical option if minimizing weight matters, while the steel model provides the more traditional all-metal sports-watch configuration. Otherwise, you’re getting essentially the same functional package.
Solar doesn’t mean automatic time correction
One specification is worth noticing if you’ve associated modern Edifice watches with Bluetooth connectivity. These models use conventional quartz timekeeping rated at ±20 seconds per month, and Casio doesn’t list Bluetooth Smartphone Link or radio-controlled time adjustment for the EFS-S660.
Solar power therefore addresses charging, not synchronization. The watch can keep itself powered through exposure to light, but it won’t automatically correct its time using your smartphone.
For buyers who specifically want automatic time correction or smartphone connectivity, other Edifice models will be a better fit. For someone who prefers a conventional analog chronograph without an app or connected service, that simplicity may instead be part of the attraction.
Which EFS-S660 should you buy?
The EFS-S660PB-1A makes more sense if you want the lightest version and prefer the sportier combination of a resin band, dark case treatment, and red chronograph hand. At 71 grams, it saves 58 grams compared with the bracelet model without sacrificing the core functions.
The EFS-S660D-1A is the better fit if you prefer a traditional stainless-steel sports watch and don’t mind the additional weight. Functionally, there isn’t much separating the two, so band material, weight, and styling are the deciding factors.
Price: ¥33,000 (About $210 USD)
Where to Buy: Casio
More broadly, both are aimed at buyers who want a compact analog chronograph without giving up solar power, sapphire crystal, a date display, or 100-meter water resistance. If the size of typical motorsport-inspired watches has been the problem, the EFS-S660’s 38.3mm case is the specification that changes the proposition.
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