Short answer
"Portugieser Automatic 31" is not an official IWC name. In replica listings it is shorthand for the Portugieser Automatic built around a copy of the 31-jewel Caliber 52010, the 42mm piece with small seconds at 9 and a power reserve scale at 3. So when a seller writes 31, they are usually telling you which movement family the watch is imitating. That matters more than any photo, because the movement is where the real gap sits between a $280 copy and a $600 one.
What the number points to
The genuine 52010 is a Pellaton-wound automatic with 31 jewels and a seven-day reserve. Few replica movements get anywhere near that. What you normally find inside is a generic automatic with a decorative plate, and a power reserve hand that is driven by the going train rather than the mainspring. It still sweeps. It just does not tell you the truth about how much wind is left.
Some sellers use 31 as a batch or version code instead. Ask directly. A vendor who cannot tell you what the number means is a vendor who cannot tell you what is in the case.
Case and dial checks from photos
I look at four things first, all visible without a loupe.
- Applied numerals: genuine Portugieser numerals are polished and stand proud with crisp edges. Cheap copies look painted or flat.
- The rail track: the minute track should be sharp and evenly spaced all the way around.
- Small seconds at 9: the subdial should be recessed, not printed flush on the dial.
- Case flanks: 42mm wears large. If the lugs look thick and slab-sided in a straight-on shot, the case is wrong.
Before you pay
- Ask for a movement photo, not a stock image.
- Ask for a running video with the crown pulled to set position.
- Confirm the lug width and strap type, since that is a common bait-and-switch.
- Check the return window. Anything under a week is not a return policy.
Price bands
Under $200 buys you a case and a dial. Between $300 and $550 you start seeing better finishing and a movement worth servicing. Above that you are paying for a specific factory run, and you should be getting documentation of it. None of these are the real thing, and none of them will hold value. Buy the one you will enjoy wearing.