Watch reference library
Cartier Tank Must SolarBeat WSTA0122
In production 2021 to present.
Specifications
- Case size
- 33.7mm x 25.5mm, 6.6mm thick (large model)
- Case material
- Stainless steel case and bracelet
- Bezel
- None, rectangular case with no rotating bezel
- Dial
- Silvered dial with perforated Roman numerals that admit light to the solar cell beneath, blued-steel sword-shaped hands
- Movement
- Cartier SolarBeat photovoltaic movement
- Power reserve
- Not applicable; charges continuously from ambient light rather than a conventional mainspring
- Water resistance
- 30 meters
- Crystal
- Sapphire crystal
- Bracelet
- Stainless steel bracelet with folding buckle
The story
The Tank Must name goes back to 1977, when Cartier used it for a more accessible, industrially produced Tank line made in silver rather than gold, part of the brand's Must de Cartier response to the quartz crisis and the first time the Tank shape was offered outside precious metal. Cartier revived the Tank Must name as a full model family at Watches and Wonders 2021, releasing extra-large, large, and small steel cases. The large and small sizes in that 2021 relaunch introduced Cartier's SolarBeat movement, a photovoltaic quartz caliber that draws power from ambient light rather than a battery that needs periodic replacement. To let light reach the solar cell without altering the dial's appearance, Cartier perforated the printed Roman numerals so they function as a light path while still reading as solid numerals to the eye. Cartier states the movement is rated for roughly 16 years of use before the cell needs replacing. WSTA0122 is the current steel bracelet configuration of the large SolarBeat model, sitting alongside the automatic caliber 1847 MC large Tank Must on strap or bracelet as the two mechanical and quartz options within the same case size.
What to check before you buy
Confirm the movement type stated on the papers or caseback, since the large Tank Must is sold with both the automatic caliber 1847 MC and the SolarBeat photovoltaic movement in visually similar cases, and only the SolarBeat versions use the perforated-numeral dial construction. Because SolarBeat has no conventional mainspring or power reserve, do not expect the watch to run down and restart the way a mechanical piece does, it simply stops if kept in total darkness for an extended period and restarts once exposed to light. There is no service-critical mainspring to overhaul, but ask whether the solar cell has ever needed replacement on an older example.
Buying or selling a WSTA0122?
Moda is always buying. Text photos to (605) 521-2821 for a fast offer, or start on the Moda Watches page. For any deal with a stranger, Moda's middleman service inspects the watch before money changes hands.
Common questions
What is SolarBeat and how is it different from a normal quartz movement?
SolarBeat is a photovoltaic movement that converts ambient light into electrical power, rather than drawing on a replaceable battery, and Cartier rates it for around 16 years of use.
Why does the dial have perforated numerals?
The perforations let light pass through the dial to reach the solar cell mounted underneath, while still appearing as solid Roman numerals from the front.
Is the Tank Must SolarBeat the same as the automatic Tank Must?
No, the large Tank Must is offered with both the automatic caliber 1847 MC and the SolarBeat photovoltaic movement in the same case size, and the reference number and dial construction differ between the two.
How water resistant is this watch?
It is rated to 30 meters, adequate for incidental splashes but not for swimming or diving.
Does the Tank Must name have historical significance?
Yes, Cartier first used the Tank Must name in 1977 for a lower-cost, industrially produced Tank in silver, and the name was revived for this steel collection at Watches and Wonders 2021.