Quick answer

A fake Datograph Up/Down is a replica of the A. Lange & Sohne Datograph Up/Down, the 41 mm flyback chronograph with an outsize date and a power reserve display. The genuine watch runs the in-house L951.6 calibre. No replica uses it. Every copy on the market runs a modified outsourced chronograph movement, so the tells show up in the dial layout, the date font, the power reserve scale, and the case finishing. Check those four areas first and you will separate a decent copy from a bad one inside a minute.

What the genuine watch does

The Up/Down arrived in 2012 as an update to the 1999 Datograph. The name refers to the power reserve indicator marked AUF and AB, read from the small seconds subdial at 8 o'clock. The rest of the layout is a date window at 12 and a 30 minute counter at 4. The case measures 41 mm across and 13.1 mm thick, offered in platinum and pink gold. The movement is hand wound, beats at 18,000 vph, carries 454 parts, and holds a 60 hour reserve. Those numbers matter. A replica that misses the diameter, the thickness, or the hand stack will not fool anyone who has handled the real thing.

Dial tells on a fake Datograph Up/Down

  • Date aperture. Genuine watches use two separate discs that jump into one window with tight edges and flat topped numerals. Copies use a single printed wheel with softer type and a wider gap.
  • Subdial positions. Genuine places the running seconds and power reserve at 8, the chronograph minutes at 4. Copies often swap the two or set them too close to the centre.
  • Power reserve hand. Genuine uses a thin hand sweeping a clean AUF to AB scale. Copies use a thicker hand or a printed arc that never moves.
  • Print quality. Genuine text sits sharp under a loupe. Copies show fuzzy edges and uneven spacing on the brand name.

Movement tells

Look through the sapphire back. The L951.6 shows Glashutte ribbing on the bridges, blued steel screws, screwed gold chatons, and a hand engraved balance cock. Replicas run a Seagull ST19 or a similar outsourced chronograph, sometimes with added date and power reserve modules. The engraving on those copies is stamped or laser etched, so the pattern repeats with uniform depth. The screws are plated, and the chatons are cosmetic rings pressed into the plate.

Case and finishing tells

  • Bevels. Genuine case edges are polished by hand and catch light in a straight line. Copies show rounded, washed out edges.
  • Pushers. Genuine pushers travel with firm resistance and reset with a clean click. Copies feel mushy and sometimes stick.
  • Weight. A platinum Datograph on a strap sits well over 100 g. Steel copies feel far lighter in the hand.
  • Crown. Genuine crowns are signed and sit flush. Copies are often oversized and sit proud of the case.

How to check a replica Datograph Up/Down step by step

  1. Measure the case across the bezel at the 4 and 10 o'clock points. It should read 41 mm. Copies often land at 39 mm or 42 mm.
  2. Measure the thickness at the crown. Genuine is 13.1 mm. Anything over 14 mm is a red flag.
  3. Set the date and watch both discs. Two independent discs should jump into one window.
  4. Wind the watch 30 turns and follow the power reserve hand. It should track from AB to AUF without sticking.
  5. Start the chronograph, then press the lower pusher to test the flyback. The seconds hand should snap to zero and restart in a single press.
  6. Turn the watch over and inspect the balance cock under a loupe. Hand engraving shows tool marks. Stamped copies look uniform.
  7. Check the screws and chatons through the caseback. Blued steel and gold are genuine. Plated steel is not.
  8. Weigh the watch on a kitchen scale and compare it against the metal the seller claims.
  9. Ask for a timestamped video of the running watch, with the chronograph engaged, before you send any money.

Price bands and what they buy

Copies under 150 USD use printed dials, a single date wheel, and a basic quartz or low grade automatic. The 200 to 400 USD band adds a real chronograph movement and a working date, but the power reserve is still fake. Above 500 USD you get better case work, sapphire crystal, and a movement with a functioning power reserve display. None of these bands gets you close to the L951.6 architecture.

Questions to put to a seller

  • What movement is inside, and can you show a photo of the balance cock?
  • Does the power reserve hand move when I wind the watch?
  • What are the exact case diameter and thickness in millimetres?
  • Can you send a video of the flyback reset?

Treat every answer as a data point, not a promise. Copies get described with loose language, and the only proof is a clear photo or video of the part in question.