If you need one answer about a watch sold as IW371654, it is this: look at the back first. The IW3716 Portugieser Chronograph family runs IWC calibre 69355, an in-house automatic column wheel chronograph, and that movement is visible through a sapphire display back. A seller offering a solid steel back or a generic chronograph has already answered the question for you. The criteria below cover case back engraving, the movement, dial and subdial layout, case and pusher finishing, and the box and papers. Each one lists the trade off of relying on that check alone, and the guide closes with a note on when a replica is the more practical purchase.
Case back engraving and the reference number
On IW371654 the reference, the serial number and the IWC wordmark should be engraved into the steel. Under raking light the letters show depth and a slight bevel at the edge of each stroke. A flat lasered print, a sticker, a mismatched font, or a serial that does not repeat elsewhere on the watch points to a fake.
- Pros: free, fast, needs no tools, and it removes the budget fake that hides a generic chronograph behind a solid back.
- Cons: a laser can copy engraving, and listing photos seldom show enough depth to judge. Treat this as a filter, not a verdict.
The movement behind the display back
This is the strongest check available to a buyer. IW371654 belongs to the IW3716 generation, which uses calibre 69355, built in Schaffhausen, with a column wheel and finishing that a stock ETA or Seagull chronograph does not match. Earlier Portugieser Chronograph references in the IW3714 family used calibre 79350, a Valjoux 7750 base, behind a closed back. A seller who describes an IW371654 with a 7750 and a solid back is describing a different watch.
- Pros: rotor engraving, column wheel and bridge finishing are costly to reproduce at this level, so the movement is hard to fake well.
- Cons: you need a loupe, good light and reference images, and a listing photo can be borrowed from another watch.
Dial printing and subdial layout
The Portugieser Chronograph is a bi-compax design, with the elapsed minutes counter at 12 and small seconds at 6, feuille hands, and applied Arabic numerals with polished facets. Compare stroke weight, numeral shape, hand length and the spacing between the subdials against photos of the exact reference. Fakes often place the subdials correctly and then fail on typography: heavier printing, uneven gaps, or a chronograph seconds hand that stutters as it sweeps.
- Pros: printing quality and hand proportions are the hardest details for a replica maker to match, and they show in any clear photo.
- Cons: dial variants exist across the reference family, so you must match photos to the exact reference rather than a sibling model.
Case, crown and pushers
Run a finger along the flanks and the lugs. IWC alternates brushed and polished surfaces with a defined line where the two meet, and the case edges stay sharp through the lug tips. The crown and the two pushers should sit close to the case with little play, and each pusher should return with a short, even click. A crown that wobbles or pushers that grind suggest a case made from a generic blank.
- Pros: touch and sound are difficult to fake without the original case tooling.
- Cons: subjective, and a genuine watch that has seen a heavy polish can feel soft in the same places.
Box, papers and provenance
Reference IW371654 should arrive with the IWC box, a warranty card or digital record, and a serial that matches the case back. Ask for an authorized dealer invoice, a service record, or a seller with a written return policy. Serial consistency across the case back, the card and the movement is the detail most fakes get wrong.
- Pros: the cheapest insurance in the process, and it is easy to verify before money changes hands.
- Cons: boxes, cards and booklets are sold on their own every day, so paperwork alone proves nothing.
When a replica is the practical buy
If what you want is the Portugieser silhouette on the wrist, a high end replica of IW371654 gives you the bi-compax dial, the steel chronograph proportions and the wrist presence of the original. What it does not give you is IWC service, water resistance you can trust, resale value, or a simple moment at customs.
- Pros: the look and the feel at a fraction of the outlay, with no dealer relationship or waiting list involved.
- Cons: no manufacturer service, unknown water resistance, no resale market, and import risk in some countries.
Buy the genuine watch if you want the calibre, the service network and the resale. Buy a replica if the watch is a costume piece and you accept those limits going in.
The order to run these checks
- Case back: engraving quality, reference number and serial.
- Display back and movement: calibre 69355 rather than a generic chronograph.
- Dial and subdials against official photos of the exact reference.
- Case finishing, crown seating and pusher action.
- Box, papers and a serial that matches across every item.