Answer
Fake A. Lange & Söhne platinum watches exist. Most use stainless steel cases with platinum-colored plating. Genuine platinum cases carry a Pt950 stamp and weigh more. A magnet test is not reliable. X-ray fluorescence (XRF) at a jeweler gives a definitive answer.
Weight and density
Platinum density is 21.45 g/cm³. Steel density is 7.85 g/cm³. 18k gold density is about 15.5 g/cm³. A platinum case weighs about 2.7 times a steel case of the same size. Weight is a first check. It is not proof.
Hallmarks
Genuine A. Lange & Söhne platinum cases have "Pt950" engraved on the caseback. The stamp sits near the case number. Some models also have a German hallmark. A fake may have no stamp. A fake may have a stamp with wrong font, wrong depth, or wrong position. A stamp alone does not prove authenticity. Fake makers copy stamps.
Movement
Genuine Lange movements have a hand-engraved balance cock. The engraving shows a floral pattern. The pattern is unique to each watch. Genuine movements use gold chatons, blued screws, and a German silver three-quarter plate. Fakes use mass-produced movements. Fake engraving looks stamped or laser-cut. Fake gold chatons are often plastic or gold-plated brass.
Price
A genuine platinum Lange 1 costs about $50,000 at retail. A platinum Datograph costs about $100,000. A fake costs $500 to $2,000. A "platinum" fake at $1,500 is not platinum. The metal alone costs more.
Serial number
A. Lange & Söhne keeps records of every serial number. Contact Lange with the case number and movement number. Lange confirms the original case material. A fake serial number does not match any record. Lange does not disclose records to third parties without proof of ownership. So this step works for buyers who already own the watch or have a seller's cooperation.
Visual checks
Platinum has a gray-white color. It does not tarnish. Rhodium-plated steel looks similar. A scratch test is not reliable. Platinum scratches. Steel scratches. Color alone cannot separate them.
Verification steps
- Weigh the watch. Compare to published specs for the model. Lange publishes case dimensions, not weight. Use density ratios.
- Ask a jeweler for an XRF test. XRF reads the metal surface. It reports platinum, gold, or steel.
- Check the Pt950 stamp. Look at font, depth, and placement.
- Inspect the movement. Look at the balance cock engraving. Look at the chatons and screws.
- Contact Lange with the serial number. Request confirmation of case material.
Limits
No single check is perfect. A fake can use a real platinum case and a fake movement. A fake can use a real movement in a steel case. XRF tests the surface. A thick platinum plating reads as platinum. A full XRF test with specific gravity measurement is more reliable. Few jewelers offer that.