Short answer

A fake Datograph Lumen is a copy of the A. Lange & Söhne Datograph Up/Down Lumen, reference 405.034. Lange built 200 pieces in 2016. The case is platinum and measures 41 mm across. The dial is a sapphire disc, not metal. Copies sell online in the low hundreds of dollars. None of them use a Lange movement, a real sapphire dial or a working outsize date mechanism.

What the original is

The Datograph arrived in 1999. It was the first chronograph movement built in-house by Lange after the company restarted in 1994. The Up/Down version followed in 2012 with a 60-hour power reserve and an indicator marked AUF and AB. The Lumen version came in 2016: platinum case, 41 mm, 200 pieces, reference 405.034.

The sapphire dial

On a standard Datograph the dial is metal. On the Lumen the dial is sapphire crystal. Luminous material sits under the sapphire. Lange masks that material so the glow appears at the outsize date numerals and the marked hours. The rest of the dial stays dark in a dark room. The sapphire is semi-transparent, so the date discs and part of the mechanism show through it in daylight.

Checks that separate a real watch from a fake

Glow under UV

Use a UV torch in a dark room. A real Lumen shows a tight, masked glow at the date and the hour marks. Most copies light up across the whole dial, or show a painted glow with uneven edges. A copy that glows over the entire dial is wrong.

Outsize date

Lange uses two separate date discs. Both jump at midnight. The numerals are narrow and the two digits sit tight in the aperture. Copies use one disc, a printed date or a slow-rolling date. Font width and the gap between the digits are the first things that look wrong in photos.

Subdials and layout

The Datograph Up/Down has two subdials set low on the dial near 4 and 8 o'clock, the outsize date at 12 and the power reserve arc at the bottom. Spacing is fixed by the movement. Copies shift the subdials by 0.5 mm to 1 mm, and the date window sits too high or too low.

Movement

The genuine watch is hand-wound. Winding feels smooth and the crown is small. The movement has hundreds of parts, a column wheel and a minute counter that jumps at 60 seconds. Finish includes Glashütte ribbing on a German silver plate and a hand-engraved balance cock. Copies use a generic automatic or quartz movement. A quartz copy has no sweep, no flyback and a crown that sets the hands and nothing else.

Case and weight

Platinum is dense. A genuine Lumen case feels heavy for its size. Steel and gold copies feel light. Check the lugs and the pushers: Lange pushers are rectangular with a shallow step, and the caseback engraving is fine and deep.

Price signals

Genuine Datograph Lumen pieces trade at auction for figures in the hundreds of thousands of dollars. The exact number changes at each sale. Listings that show a Lumen for a few hundred dollars are copies. Lange does not publish a public serial database, so a service check by the maker or a specialist is the last step before money changes hands.

What replicas can and cannot do

A high-end replica can copy the case shape, the dial print and the strap. It cannot copy the sapphire dial with masked luminous coating, the twin jumping date discs, the column wheel chronograph or the hand engraving. Buyers who want the look at low cost accept those gaps. Buyers who want the function need the real watch or a different model.