Short Answer

A fake Omega 3320 is a watch that claims the 3320 chronograph calibre but holds something else inside. The real 3320 is an automatic chronograph built on an ETA 2892-A2 base with a Dubois-Depraz chronograph module stacked between the movement and the dial. It runs at 28,800 vibrations per hour, which is 8 beats per second, and carries 25 jewels. Replicas substitute a Chinese 7750 clone, a Seagull ST19 hand-wind, a mecaquartz module, or a plain quartz calibre. Because the Speedmaster Date has a solid caseback, no outside inspection proves the movement. You confirm the real thing by beat rate, chronograph sweep, pusher feel, case thickness, and rotor engraving with the back removed.

The Real 3320 in Plain Numbers

  • Base calibre: ETA 2892-A2, automatic winding, 21 jewels before the module is added.
  • Total jewel count: 25.
  • Frequency: 28,800 vph, 4 Hz, 8 beats per second.
  • Power reserve: about 42 to 44 hours.
  • Chronograph: modular, cam switched, mounted as a separate plate above the base movement.
  • Hands: running seconds at 9, chronograph minutes at 12, chronograph hours at 6.
  • Rotor: engraved with the Omega name and calibre number. Finish varies by production run.
  • Close relative: the earlier Omega 1152-series chronograph calibres use the same stacked architecture.

How to Check a Watch Step by Step

  1. Start the chronograph and run it against a phone stopwatch for a full 60 seconds, then compare the 30-minute totalizer at 12 o'clock. Drift inside one minute points to a poorly regulated or non-mechanical movement.
  2. Hold the watch to your ear and count the balance beats for 10 seconds. A real 3320 gives 80 beats. A 21,600 vph clone gives 60. A quartz movement gives one tick per second.
  3. Watch the center chronograph hand for 10 seconds while it runs. A mechanical 3320 sweeps at 8 steps per second. A quartz chronograph jumps once per second. A mecaquartz module jumps five times per second.
  4. Press the upper pusher. The Dubois-Depraz module has a short, light travel with a clean click. A 7750 clone feels stiff and needs a longer push.
  5. Press the lower pusher to reset. All three chronograph hands should snap to zero at the same instant and stay there.
  6. Measure the case thickness with calipers. The modular movement sits tall, but a 7750-based fake sits taller still, often 1.5 to 2 mm over the factory figure.
  7. Pull the crown to the date position and step through a full month. Each increment should snap over with no partial engagement and no backwards creep.
  8. Take the watch to a watchmaker and open the caseback. Read the rotor engraving, count the jewels at the balance, and confirm that the base plate and the chronograph module are two separate stacked assemblies.

Red Flags That Point to a Fake

  • The seller describes the movement only as "Swiss" and never gives a calibre number.
  • The seller refuses an open-caseback inspection before payment.
  • The rotor engraving is shallow, off-center, or missing the jewel count.
  • The chronograph hand stutters at start or resets without a firm click.
  • The case measures noticeably thicker than the reference it copies.
  • The date changes slowly across several minutes instead of snapping over.

Questions to Ask Before You Buy

  1. Ask which calibre number is stamped on the rotor, and ask for a photo of that stamp.
  2. Ask for a timegrapher reading in six positions, not a single number.
  3. Ask for the measured case thickness in millimeters.
  4. Ask whether a watchmaker can open the caseback before money changes hands. A seller with a real 3320 will say yes.

Bottom Line

Treat "3320" on a listing as a claim, not a specification. The number means a specific 2892-based automatic chronograph with a stacked module, and that architecture leaves physical evidence: 8 beats per second, a light modular pusher feel, a defined case thickness, and engraving on the rotor. Verify any one of those and you learn more than a page of marketing copy tells you.