Short answer
Photos cannot prove that a pre-owned A. Lange & Söhne is original. The decisive test is the movement. Lange builds every caliber in Glashütte, cuts the main plate from untreated German silver, and finishes each balance cock with hand engraving that differs from every other watch. A fake usually fails on those three points, on the screw and chaton details, and on the numbers stamped inside the caseback.
Prerequisites
- A 10x loupe and a bright diffused light source.
- A scale accurate to 0.1 g.
- The box and guarantee booklet, if the seller still has them.
- Written return rights and a payment method you can reverse.
How to authenticate a pre-owned Lange
- Match the reference number stamped on the caseback against Lange's published model list. Confirm that the reference exists and that it was offered in the case material you are holding.
- Weigh the watch on the scale. Gold Lange cases carry a 750 stamp and platinum cases carry Pt950. A steel case on a routine reference is a fake, because steel Lange watches exist only as rare one-offs.
- Study the dial and hands under the loupe. Printing should be crisp with no ink spill, applied markers should have sharp polished bevels, and blued steel hands should show a deep uniform blue with no paint edges.
- Turn the watch over and read the movement plate. Genuine three-quarter plates are untreated German silver, a warm pale yellow-grey, engraved with the maker name, Glashütte I/SA, Made in Germany, the jewel count, and the movement serial. Fake plates are plated brass with a cool white tone and shallow laser lettering.
- Inspect the balance cock engraving with the loupe held at an angle. Hand engraving changes depth along each cut and follows a floral pattern unique to that watch. Laser engraving stays flat and repeats the same pattern across every example of the caliber.
- Check the screws and jewel settings. Lange uses heat-blued steel screws and screwed gold chatons, so the bluing sits in the metal and the chatons are held by their own small screws. Painted blue heads and plain holes indicate a copy.
- Compare the movement serial with the case number and the guarantee booklet. Both numbers appear in the papers and in any Lange service record, and they must match each other and the production era of the reference.
- Send the watch to Lange or to a watchmaker trained on German movements. A service inspection under a stereo microscope confirms the finishing and the numbers and gives you documentation you can keep.
Red flags that end the inspection
- Swiss Made printed anywhere on a Lange.
- A price far below current auction results for the same reference.
- A smooth plate with no engraving or an ETA-based movement under the rotor.
- A seller who refuses a pre-purchase inspection or a conditional return.
Make any offer conditional on authentication. A seller with a genuine watch will accept the condition, and a seller with a copy will not.