The short answer
830107 is not a Cartier reference number. Cartier's catalog runs on codes like WSTA0041 or W5200005, so a six-digit number on a listing page almost always comes from the seller's inventory sheet or a factory batch log. It identifies a specific build that seller ordered. It is not a spec sheet you can look up. Two sellers can post the same 830107 and ship watches that differ in thickness, movement and dial print. The code is a starting point, nothing more.
Treat it like a lot number. Your job is to confirm what is inside that lot.
Anchor the listing against real Tank dimensions
Cartier builds the Tank in several families, and each has its own footprint. A replica reads as convincing only when the case matches the real one on both axes and in thickness.
- Tank Must large: about 33.7 by 25.5 mm. Small: about 29.5 by 22 mm.
- Tank Solo large: about 34.8 by 27.4 mm. Small: about 31 by 24.4 mm.
- Tank Louis Cartier large: about 33.7 by 25.5 mm, with a slimmer profile than the steel models.
- Tank Francaise: roughly 30 by 25 mm in medium and 25 by 20.5 mm in small, with a curved case that wraps the wrist.
Pull the numbers from Cartier's own site for the model the seller names, then compare. A 1.5 mm difference in height sounds trivial. On a Tank it shows, because the case is a flat rectangle resting on a flat wrist.
Quartz is not a red flag by itself
This trips people up. The genuine Tank Must and the entry Tank Solo run on quartz movements, so a quartz replica of those references is mechanically honest. Where it goes wrong is a quartz movement inside a watch sold as a Tank Louis Cartier or a Tank Francaise automatic. Those should be mechanical. Ask the seller what powers the watch and what the case back says. Vague talk about a Swiss movement with no caliber number is a signal.
Details worth inspecting
- Crown cabochon. Genuine Tanks use a blue spinel. Cheap builds use painted resin that looks flat and purple under indoor light.
- Dial print. Roman numerals should be crisp and evenly spaced. Fuzzy edges around the VII or the minute track show up fast in photos.
- Hidden signature. Cartier tucks a tiny CARTIER word inside one of the Roman numerals, most often the VII on a Tank. It should be present and sharp under magnification, not stamped as a blob.
- Hands. Blued steel or polished steel, depending on the reference. A painted finish with a purple cast reads wrong.
- Case back. Engraving should be centered and cut clean. A listing photo showing a made-up model string is a giveaway.
- Thickness. A slab-sided case that sits tall above the wrist is the most common tell on budget builds.
- Strap. Alligator-grain leather is standard on most Tanks. Check the taper and that the pin buckle is finished to match the case.
Questions I would ask before paying
- What are the exact case dimensions in millimeters, including thickness?
- What movement is inside, and is it quartz or mechanical?
- Is the crystal sapphire or mineral glass?
- Can you send a wrist shot and a side profile shot, not just a front-on catalog image?
- What is the return window if the watch arrives off spec?
If a seller cannot answer the first three, the 830107 code does not matter.
The legal side
A replica is not a Cartier. It carries no manufacturer warranty, no service history and no resale value. In the United States, counterfeit goods are subject to seizure by Customs and Border Protection, and selling them can expose a seller to trademark liability. Worth knowing before you spend money, whatever the listing claims about quality.