Short answer

On replica listings, "3604" is rarely an official Omega reference number. It is a seller or factory code, pasted into titles to group one batch of watches. Two shops can attach the same digits to two different cases, so the number alone tells you nothing about quality. Use it as a starting point, then confirm the things that actually matter: case diameter, movement, dial layout, bracelet type, and the caseback engraving.

How to figure out which watch you are looking at

Start with the photos, not the title. Sellers build titles from factory batch codes because those codes already carry search volume. The watch behind them is usually a mainstream model: a Seamaster-style diver, an Aqua Terra-style three-hander, or a Speedmaster-style chronograph.

Three details separate those quickly. A dive watch has a rotating bezel, a screw-down crown, and often a helium escape valve at 10 o'clock on the 42mm versions. A three-hander on a steel bracelet with a teak-pattern dial is the Aqua Terra look. A chronograph with two registers and a tachymeter bezel is the Speedmaster look. Measure across the bezel and compare the number to the model you actually want.

What to verify before you order

Movement

Ask for a photo of the movement inside the actual watch, not a stock image. Most three-handers at this tier run an Asian 2824 or 2836 clone. Chronographs usually use a 7750-based movement. Better builds use a decorated clone that mimics the Omega rotor and bridge shapes. A decorated movement is not a co-axial escapement, so treat service intervals like any standard Swiss-style automatic.

Dial and hands

Check the date window position against the movement. A 2824 puts the date at 3 o'clock. A 2836 changes the layout if a day wheel is involved. Look at the logo: printed ones sit flat under light, applied ones catch an edge and throw a shadow. Lume should read pale cream or white in daylight, not butter yellow. On diver dials, the bezel triangle has to sit centered at 12.

Case and crystal

Look for sharp lugs, an even brushed finish on the flanks, and a polished chamfer that runs the full length of the case. Anti-reflective coating should kill reflections without giving the crystal a blue haze. Water resistance claims mean little here. A replica diver is fine for rain and hand washing, and I would not swim with one unless a watchmaker pressure-tests it first.

Bracelet and clasp

Solid end links that sit flush against the lugs are the mark of a better build. Hollow links leave a visible gap and rattle when you shake the watch. The clasp should close with one clean click and the safety latch should snap shut. Engraved markings should be deep enough to catch a fingernail. Bracelet screws should take a proper screwdriver without stripping the slot.

Price bands and what they buy

Under about $80 you are buying a novelty. The movement finishing is rough, the crystal is mineral, and the bracelet is stamped. Between $150 and $300, decent builds show up: sapphire glass, a reliable 2824 or 2836, solid links, and a clasp that feels like a clasp. Above $400 you are paying for closer dial details, better lume, and a decorated movement. Returns fall off fast past that point.

Quick checklist

• Case diameter and lug width confirmed against the model you want
• Movement photo from the actual watch, not a catalog shot
• Date window position matching the movement inside
• Applied logo, correct lume color, centered bezel triangle
• Solid end links, aligned brushing, working clasp safety
• Sapphire crystal with even AR coating
• Seller answers questions and accepts returns before payment

What to keep in mind

These watches are not made by Omega and come with no factory warranty. Genuine parts will not fit, and a local watchmaker may decline to service one. Customs can seize shipments of goods carrying protected trademarks, so ordering from overseas carries real risk. If you want a watch you can swim in, hand down, or resell, that money goes further on a mid-range Swiss or Japanese piece. If you want the look on a small budget and you accept the trade-offs, the checks above are what keep you from overpaying.

Bottom line

Forget the 3604 code. Match the photos to a real model, verify the movement and the bracelet details, and judge the seller on how they answer questions. That tells you far more than any number in a listing title.