Short answer
IW938604 is not a reference number in IWC's catalog. Watches sold under that number are replicas. The controls follow the movement inside the case, not the name on the dial. Most replicas sold with this number use a clone of the ETA 7750 chronograph or the ETA 2824 automatic. Crown positions, winding direction, and pusher layout come from those two movements.
Fake IW938604 Comparison: Real vs Replica Checkpoints
Step 1: Identify the movement
Look at the dial and the caseback before you touch the crown.
- Subdials at 6, 9, and 12 with a running center seconds hand: ETA 7750 clone. Pushers at 2 and 4 o'clock.
- Center seconds with a date window at 3 and no subdials: ETA 2824 clone. Crown only, no pushers.
- Shake the watch. A 7750 clone has a rotor that spins in one direction and winds in the other. The wobble is visible.
Step 2: Wind and set
- Shake the watch 10 to 15 times to free the rotor oil after storage. Shake again. Then wind by hand.
- Unscrew the crown if it sits on a threaded tube. Turn it counterclockwise 3 to 4 turns until it releases.
- Position 0: turn the crown clockwise 25 to 30 turns. A 7750 clone reaches near full wind at that count.
- Pull to position 1 for the date. Turn one direction for the date, the other for a day wheel if fitted. Do not change the date between 9 p.m. and 3 a.m. The date finger can jam the calendar wheel.
- Pull to position 2 for the hands. Push the hands past 12 to find midnight, then set the correct time.
- Push the crown in and screw it down. A crown left loose breaks the gasket seal.
Step 3: Run the chronograph
The pusher at 2 o'clock starts and stops the sweep hand. The pusher at 4 o'clock resets it to zero. Reset with the chronograph stopped. Pressing reset while the hands run can strip the reset wheel and the heart piece. Do not use the chronograph for more than a few hours at a time. Constant running drains the mainspring and adds wear on the vertical clutch or the cam.
Water and service
Replica cases carry printed ratings of 30 m to 50 m. Those numbers cover splashes, not swimming. The gaskets on most replicas are thin and dry out. Keep the watch away from showers, pools, and salt water. A 7750 clone runs 42 to 48 hours on full wind. A 2824 clone runs about 38 hours. Send the watch for service every 3 to 5 years, or when it loses more than 15 seconds a day.
Limit of this guide
No factory spec sheet exists for IW938604. Confirm the movement type from the caseback engraving or a watchmaker's inspection before you set the date or run the chronograph.