Short answer
"Fake IW329040 V5" means a replica of the IWC Aquatimer Automatic, reference IW329040, built by a workshop that labels its fifth revision V5. The number tracks how many times the maker reworked the case, dial or movement. It is not a grade handed out by IWC or anyone else. A V5 can be better than a V4 and still be a bad watch. You have to read the photos and video for the specific piece.
What the real one is
The Aquatimer Automatic is a 42 mm steel dive watch with an internal rotating bezel and IWC's SafeDive setup, where the outer ring drives the inner scale so the crystal stays clear. Water resistance on the genuine is rated to 300 m. Sapphire crystal, screw-down crown, bracelet or rubber strap depending on the version. Learn those specs before you look at any replica, because that is what the fake gets measured against.
What V5 usually gets right
Case proportions and crown guard shape are close on most V5 batches. The bezel grip pattern reads correctly at arm's length. Dial printing on recent runs is respectable, with applied markers sitting flat and lume plots centered in their surrounds. Steel finishing on the flanks holds up. If you have handled an older revision, the improvements show up in small places: font weight, hand finishing, how the date sits inside the window.
Where it usually falls short
- Bezel action. Genuine SafeDive feels geared and tight. Replicas often feel loose or gritty, and some have visible play between the outer ring and inner scale.
- Lume. It fades faster and often skews slightly green next to a real dial.
- Water resistance. Treat 300 m as a claim, not a fact. Have it pressure tested before it goes near water.
- Movement. Normally a decorated Asian automatic rather than IWC's caliber. Timekeeping is fine; rotor noise usually is not.
- Caseback engraving and serial depth. This is the tell when the watch is in your hand.
How I check one before paying
Ask for dated photos on a plain background, then a short video of the bezel turning and the second hand sweeping. Request a lume shot in a dark room and a close-up of the caseback. Compare the dial layout against IWC's product page for the reference, marker by marker. A seller who will not send a bezel video is telling you something useful.
Price is the second signal. If one V5 undercuts every other listing by a wide margin, that is a warning, not a deal.
Living with it
Keep it out of chlorine until it has been tested. Rinse it after salt water. Expect the gaskets to be the first thing to fail. And treat the V5 label as the start of a conversation about one specific watch, not a promise about the one in the box.