Quick answer

A fake A. Lange & Söhne Datograph Up/Down is graded on the three features the real watch is built around: the 41 mm case, the outsize date at 12 o'clock, and the power reserve hand on the up/down scale. If the date font is wrong, the power reserve hand never moves, or the chronograph minute counter drags instead of jumping, the watch is a low-grade copy. A high-grade replica can match the case and the dial layout. The movement is where it fails.

What the real Up/Down does

The genuine Datograph Up/Down is a hand-wound platinum chronograph, reference 405.035, 41.0 mm wide and about 13.1 mm thick. Calibre L951.6 holds 60 hours of power. Up/Down refers to the power reserve display: a hand on an AUF/AB scale in the lower half of the dial shows how much mainspring energy is left. The chronograph uses a column wheel, a flyback function, and a minute counter that snaps a full minute in one instant step. The sapphire back shows a German silver three-quarter plate, screwed gold chatons, blued screws, and a hand-engraved balance cock.

Before you inspect

  • A caliper that reads to 0.1 mm
  • A 10x jeweler's loupe
  • Bright, angled light and a dark cloth backdrop
  • Printed or saved photos of a genuine 405.035 for side by side comparison
  • Straight-on seller photos plus a clear shot of the caseback

How to check a fake Datograph Up/Down

  1. Measure the case across the bezel at 4 and 10 o'clock. The real number is 41.0 mm. Copies of this watch usually come in at 39 to 40 mm because they reuse a generic chronograph case.
  2. Measure the thickness at the center of the caseback. The genuine watch is about 13.1 mm. Anything under 12 mm or over 15 mm is wrong.
  3. Weigh the watch. Platinum is dense, and a genuine 41 mm Up/Down feels heavy in the hand. A steel replica of the same size feels light, often by 60 grams or more.
  4. Study the outsize date through the loupe. Two separate date discs, one per digit, with a clean vertical gap and a serif font. Cheap fakes print the date on a single disc or use square, heavy numerals.
  5. Set the time to 11:58 PM and watch the date change. The genuine date snaps over at midnight in one step. A slow rolling change points to a modified automatic movement.
  6. Time the minute counter. Start the chronograph with the pusher at 2 o'clock and watch the counter for one full minute. The genuine hand jumps to the next mark in a single snap. A hand that sweeps or creeps sits on a Seagull ST19 or an Asian 7750 base.
  7. Test the flyback. With the chronograph running, press the reset pusher at 4 o'clock once. The genuine chrono stops, returns to zero, and restarts on that single press. If it only resets or jams, the flyback was never built.
  8. Wind the watch fully and track the power reserve hand over several hours. It should travel a steady arc from the AUF end to the AB end. On most fakes this hand connects to nothing, or it is wired to a day/night wheel that moves twice a day.
  9. Turn the watch over. A hand-wound movement has no rotor. If you see a spinning weight or an automatic bridge, the watch cannot be a faithful copy of the Up/Down.
  10. Read the engraving on the balance cock and the three-quarter plate. Genuine parts carry deep hand engraving and Glashütte ribbing. Replicas show shallow laser etching or a plain plate.
  11. Press both pushers and feel the travel. Genuine pushers have a short throw and a crisp click. Mushy or long-throw pushers mean a generic chrono module sits inside.
  12. Compare the dial printing under the loupe. The brand mark, the minutes track, and the subdial rings hold sharp edges on the real watch. Soft or doubled printing is a spray-and-print dial.

Red flags that end the inspection

  • Case under 40 mm or over 42 mm
  • A rotor visible through the sapphire back
  • A power reserve hand that is painted on the dial with no pinion
  • A minute counter with 30 marks instead of 60
  • A single date disc with printed numerals
  • Chronograph pushers that need two presses to reset

Grade summary

Low grade: wrong case size, printed date, decoration instead of function. Mid grade: correct 41 mm case and dial layout, ST19 or 7750 base, no flyback, dead power reserve hand. High grade: correct dimensions and dial, working column wheel chrono, instant minute jump, but automatic winding or machine-finished plates that no hand-engraved Lange part would show. The back of the watch settles the argument every time.