For most buyers searching a fake Omega 3520, the best pick is a 39 mm Speedmaster Day-Date copy running a full-calendar automatic chronograph (the 7751 family or a modular 2892 base), because the triple-date dial is the entire reason this reference exists and a quartz or day-date-only build gets the layout wrong. I compared the options on four points: dial layout accuracy, case thickness and lug profile, whether the chronograph and calendar actually work, and how the bracelet sits on the wrist.

What the 3520 name covers

The number appears in two places. Omega used 3520 for the Speedmaster Day-Date, a steel chronograph with day, date, and month displays plus a 24-hour reading. Sellers also use 3520 as shorthand for any Speedmaster wearing that triple-date dial. Both readings matter, since the calendar layout is what separates a believable copy from an obvious one.

Reference points buyers compare against

  • Case: about 39 mm across, steel, with straight lugs and a slim bezel.
  • Dial: day, date, and month windows plus small counters for the chronograph and 24-hour hand.
  • Crystal: domed sapphire on the original, flat mineral or sapphire on most copies.
  • Bracelet: three-link steel with a signed clasp and correct endlink fit at the lugs.

Option 1: Full-calendar automatic (7751 or modular 2892)

This is the group that reproduces the whole point of the watch. The calendar jumps with the crown, the chronograph resets to zero, and thickness stays close to the original.

  • Pros: correct dial furniture, working day-date-month, acceptable pusher feel, easy service at most watchmakers.
  • Cons: costs more than the entry builds, and the extra calendar module adds thickness that shows under a cuff.

Best for: buyers who want the watch to behave like the reference, not just look like it from two feet away.

Option 2: A7750 day-date builds sold as 3520

Plenty of listings carry the 3520 label while sitting on a plain day-date chronograph movement. The pushers and subdials read fine, but the month window is missing or faked with printed text.

  • Pros: widely available, lower entry price, solid chronograph function, familiar parts supply.
  • Cons: wrong calendar layout, rotor noise on cheap examples, caseback engraving often mismatched to the dial.

Best for: someone who wants a daily Speedmaster look and does not care about the month display.

Option 3: Quartz copies

Battery builds trade mechanical honesty for a low price and a thin case. The seconds hand ticks, which is the first thing any Speedmaster owner notices.

  • Pros: accurate timekeeping, light on the wrist, no service cost.
  • Cons: ticking seconds hand, subdials that are decorative, hollow bracelet feel.

Best for: a costume piece worn a few times a year.

Option 4: Fantasy dials and oversized cases

Some sellers stretch the case past 40 mm, add a date magnifier, or print text that never appeared on the original. These are the builds to skip unless the price reflects what they are.

  • Pros: cheap, plentiful, sometimes offered in odd colorways.
  • Cons: wrong proportions, wrong fonts, and no resale interest.

Checklist before you commit

  1. Measure the case across the bezel and confirm it lands near 39 mm.
  2. Ask for a photo of the calendar windows mid-month to see the font and alignment.
  3. Check pusher spacing and crown size against photos of the reference.
  4. Confirm the chronograph starts, stops, and resets at zero.
  5. Look at the endlink fit at the lugs, a common weak point on copies.
  6. Verify the clasp and caseback engraving match the dial version.

Which one to choose

Pick the full-calendar automatic if the triple-date dial is what drew you to the reference. Choose the day-date chronograph if budget matters and you never use the month window. Take the quartz only as a novelty. Walk away from oversized fantasy cases, since they read wrong at arm's length and cannot be fixed with a new strap.