The IW371634 is the stainless steel bracelet version of the IWC Portugieser Chronograph: 40.9mm case, silver plated dial, two sub dials stacked at 12 and 6, slim leaf hands, five link bracelet. Replicas of this reference are everywhere, and the better ones are close enough that you need a caliper, not a hunch, to sort them out. Three things separate a $250 copy from a $500 one: case thickness, dial printing, and how the bracelet end links sit against the case. Check those and you are most of the way home.
What the real IW371634 is
Know the target before you judge a copy.
- 40.9mm steel case, about 13.1mm thick, 30m water resistance
- Silver plated dial, rhodium plated leaf hands, applied numerals, date at 3
- Chronograph with a 30 minute counter at 12 and running seconds at 6
- Double box domed sapphire crystal with antireflective coating on both faces
- Calibre 79350 in earlier production, in house 69355 from 2020, 44 to 46 hours of reserve
- Five link steel bracelet with a push button folding clasp
The dial is where most copies fall apart
Put a loupe on the minutes track. On the real dial the printed ticks are crisp, evenly spaced, and sit close to the chapter ring without crowding it. Cheap replicas smear here: ticks merge, the printing rides a little high, and the IWC signature at 12 comes out too bold. Look at the sub dials next. The snailing should be fine and concentric, and the small hands should reach the printed marks. If the chrono hand stops short of the track, or the snailing looks like a spiral drawn with a marker, walk away.
The date window is another tell. A good copy cuts the aperture clean with a beveled edge and the disc sits flush. A bad one leaves a ragged edge and the numeral floats low in the frame.
Thickness and the movement decide the price
Most cheap replicas run a stock or lightly modified Valjoux 7750 layout. Sturdy workhorse, but it pushes the case to 14.5mm or more against a real 13.1mm. That extra millimeter reads as a slab on the wrist and shows up in the caseback profile. The better tiers use a custom 69355 clone or a slimmed 7750 with decorated bridges and rotor. Ask the seller for a caliper photo of caseback to crystal, not a beauty shot. If they cannot produce one, that answers your question.
Function check: pull the crown to the first position and set the date, second position for the hands. Start the chrono, let it run past the one minute mark, and watch the counter at 12 step over. Reset and confirm both hands snap back to zero. A lazy reset or a counter that lags points to a tired module.
The bracelet carries half the look
People pick the 634 over the strap version for the bracelet, so give it the same scrutiny as the dial. Run a thumb along the outer edge of the links. Good finishing is brushed in one direction with no polish bleeding onto the sides. Flex the bracelet: it should move with slight resistance, not rattle like a chain. Then check the end links against the case. A gap at the top, or a step where the link meets the lug, is the most common flaw on mid tier copies. The clasp should close with a firm click and sit flush. A clasp that stands proud will scratch a desk inside a week.
Before you pay: the checklist
- Ask for a caliper shot of case thickness. Anything over 13.6mm is a thick case.
- Request a macro of the dial at 12 and the minutes track.
- Ask which movement it runs and whether the chrono resets to zero.
- Confirm the crystal is double AR coated. Single coating gives a blue grey glare at an angle.
- Get photos of the end link fit on both sides of the case.
- Be realistic about water resistance. Treat any replica as splash proof at best.
- Check caseback engraving depth and the serial font.
- Buy from a seller who will send a video of the running chrono.
Price tiers
- Under $150: quartz or low grade automatic, wrong sub dial spacing, hollow bracelet. A costume piece, not a watch.
- $200 to $350: 7750 based, correct layout, thick case, decent dial, bracelet is the weak point.
- $400 and up: slimmed or clone movement, double AR crystal, finished bracelet with tight end links. This is the tier worth buying if you care about the reference.
Living with it
The 40.9mm case wears like a 39 on most wrists because the bezel is so thin, but the dial looks bigger than the number suggests. Under a 6.5 inch wrist the bracelet version sits heavy, and the strap version balances better. Have the movement regulated if it gains more than 20 seconds a day, keep it away from steam, hot showers, and speaker magnets, and wipe the caseback down after wear. The crystal and the bracelet take the abuse; the dial is what you paid for.