The Luminor Due 42 is Panerai's slimmed-down take on the Luminor case, and that slimness is where most replicas fail. A usable copy gets the 42mm cushion case right. A good one also gets the roughly 10.5mm thickness, a real sandwich dial, small seconds at 9 o'clock, and the date at 3. If the case measures 13mm or more, or the dial is flat printed instead of layered, stop there.

Start with the case profile

The whole reason the Due exists is to fit under a shirt cuff. Panerai kept the crown guard and the lume but shaved the case down. Replica factories can copy the outline from photos. The profile is harder. I put calipers on the case before anything else. Steel Due 42 models sit near 10.5mm, and the caseback is a closed, screwed plate on most references. If the seller quotes 13mm or dodges the question, it is a standard Luminor rep with a new dial on top.

• Diameter should be 42mm across the cushion, not 44.
• Thickness near 10.5mm, and noticeably thinner than a Luminor Base.
• Lugs should curve down. Straight, slab lugs are a giveaway.
• Crown guard lever should snap, not flop.

Dial details that matter

The Due 42 uses a sandwich construction: a cut top plate with lume filling underneath. Hold it at an angle and you should see depth at the cutouts. The print is thin and crisp. The small seconds subdial sits at 9, the date window at 3, and on most references the date is black on white with a clean bevel. Look at the hands too. They are thin, pencil shaped, and the lume should fill them evenly without bubbles.

Movement and caseback

Genuine Due 42 models run the P.900 automatic, a three-day movement. Replicas use a decorated clone, usually a Miyota or Seagull base. That is fine if the rotor spins quietly and the watch hacks. What is not fine is a movement spacer rattling around, or a caseback engraved with the wrong reference. Ask for a photo of the caseback engraving and the movement through an open back if the model has one.

Water resistance and straps

Panerai rates the Due 42 at 3 bar, which is splash resistance, not swimming. Replicas often claim 100m and deliver nothing close. Treat any Due replica as splash only. The strap matters more than people think. Genuine watches ship on alligator or a rubber accordion, with quick-release pins on newer references. A cheap, stiff strap with plastic keepers usually signals a cheap watch underneath.

Price and red flags

Steel Due 42 replicas from decent factories land in the low hundreds of dollars. Anything under about $120 is almost always a low-grade build with a printed dial. Above $400 you are paying for a name, not better parts. Red flags: stock photos with no macro shots, refusal to show thickness, mismatched date font, and a crown guard that does not sit flush. Ask for a short video with the seconds hand running and the crown being wound. It tells you more than ten stills.