The short answer
A replica Datograph Up/Down is a counterfeit of A. Lange & Söhne's 41mm platinum chronograph from 2012. It can get the case shape, the dial layout, and the sapphire crystal close enough that someone across a table won't flinch. It cannot get the movement. The real watch runs the in-house calibre L951.6, a column-wheel flyback chronograph with a precisely jumping minute counter and a 60-hour power reserve indicator. No replica on the market reproduces that. What you get is an Asian chronograph module dressed to look German, and importing it into the US is illegal.
What the original actually is
The Up/Down is the 2012 update to the 1999 Datograph. Lange widened the case from 39mm to 41mm, added a power reserve indicator at the bottom of the dial (that is the "up/down" in the name), and stretched the reserve to 60 hours. The outsize date sits at 12. The chronograph runs on a column wheel, and the minute counter jumps the instant the chrono seconds sweep past zero instead of creeping forward. Around 400 parts, hand-finished, Glashütte ribbing on German silver. That finishing is the product. You are not buying a dial, you are buying the hundred hours of anglage underneath it.
Where replicas land, honestly
- Dimensions: most are close on paper. In hand they run thick, often 13.5mm and up against the real 13.1mm, and the lugs feel slabby.
- Chronograph: expect a modified Seagull or 7750 base. The pushers are mushy. Flyback does not exist. The minute counter often drags.
- Date: the outsize date is the tell. Real ones snap. Replicas flip slowly or leave one digit half-turned.
- Movement finishing: stamped, not engraved. No black polish, no sharp inward angles. A loupe kills it in five seconds.
- Power reserve indicator: frequently decorative or wired to a crude gear train that reads wrong at both ends.
US legal reality
Counterfeit watches infringe registered trademarks, and trafficking in them is illegal under US law. CBP seizes fake watches at the border routinely, and an order can vanish without a refund. Reselling one is a worse problem than owning one. If a seller ships from overseas with a customs declaration that says "gift" or "watch parts," that is the seller protecting themselves, not you.
If you want the look without the headache
Want a German chronograph architecture at a realistic price? Look at a used Glashütte Original Senator Chronograph, a Nomos Tangente with the smaller case, or a Stowa Flieger Chrono. You get honest finishing, a serviceable movement, and a watchmaker who will actually touch it. If the appeal is the Datograph itself, save. The real one holds value in a way no replica ever will, and it is the only version that delivers the thing you are chasing.