Short answer

A fake Jaeger-LeCoultre Master Compressor Extreme Lab fails three checks. Weight. Movement finish. Case back engraving. Grade 5 titanium has a density of 4.43 g/cm3. Stainless steel has a density of 7.9 g/cm3. A steel copy of the 46.3 mm Extreme Lab case weighs about 1.8 times more than the titanium original. Jaeger-LeCoultre released the Extreme Lab 1 in 2007 with calibre 988C. The Extreme Lab 2 followed in 2010 with calibre 780. No documented copy uses either movement.

Genuine specifications

  • Extreme Lab 1: 2007. Grade 5 titanium case. Diameter 46.3 mm. Calibre 988C. Escapement runs without oil.
  • Extreme Lab 2: 2010. Grade 5 titanium case. Diameter 46.3 mm. Calibre 780. Chronograph and second time zone.
  • Crystal: sapphire with anti-reflective coating on both faces.
  • Water resistance: 100 m.
  • Output: small batches. The line never ran at high volume.

Case back and numbers

JLC engraves two numbers on the case back. One is a reference number. One is a case number. The engraving is cut into the metal. A copy prints the number on a plate, or cuts a shallow mark with rough edges. The font on the genuine back is a sans-serif with even stroke width. Check the space between the reference and the case number. Copies show spacing that drifts. Photograph the back with a macro lens and compare stroke edges at 10x magnification.

Dial, hands and lume

The dial carries the Jaeger-LeCoultre wordmark, the Master Compressor name and the Extreme Lab designation. On the genuine dial all three lines share one baseline. Copies misalign one line. The lume plots hold an even layer of Super-LumiNova. Copies show patches and craters at the edge of each plot. Hands on the original carry polished bevels. A stamping leaves rounded edges and no bevel.

Movement

Calibre 988C and calibre 780 both carry cotes de Geneve stripes, anglaged bridges and blued screws. The Extreme Lab 1 escapement uses ceramic parts and runs with no lubricant. A copy uses a generic automatic movement, often a clone of a stock calibre. Look at the balance wheel, the rotor engraving and the screw heads. Slot edges on copy screws show burrs.

Crown, pushers and crystal

The Extreme Lab 2 uses a crown with a locking lever. Copies replace the lever with a fixed crown, or with a push-pull crown that does not seal. Sapphire has a Mohs hardness of 9. Mineral glass sits near 5.5. A drop of water beads on sapphire and spreads on glass. Anti-reflective coating on the genuine crystal cuts reflection from both faces. Copies show a strong white reflection from the front.

Price and documents

Genuine Extreme Lab watches trade in the five-figure US dollar range. Copies list in the low hundreds. That gap is the first signal. The genuine set includes a presentation box, a warranty card and a certificate with numbers that match the case. Copies ship with a generic box and a card with no matching number. A seller who refuses a case number check before payment is a risk.

Where to verify

  • Jaeger-LeCoultre boutique or an authorized service center. Ask for a case number lookup.
  • A watchmaker with a timing machine. Genuine calibres hold a rate within a few seconds per day.
  • A customs or police report if the sale involves fraud. Trafficking in counterfeit goods carries penalties under 18 U.S.C. 2320.

Limits of a visual check

Photos in a listing hide weight and movement finish. Two Extreme Lab references exist, and parts differ between them. A visual check cannot confirm a movement without opening the case back. State the result as probable, not certain.