Our top pick for a first answer is a 10x jeweler's loupe paired with a thermal or electrical diamond tester, because together they separate diamond from cubic zirconia, glass, and moissanite in under a minute and cost nothing at most jewelry counters. The criteria behind that pick: accuracy on small melee stones, no risk to fragile replica settings, and the ability to flag the one case a basic tester cannot catch, a lab-grown diamond that is real diamond but not the mined stone a seller implied.

What People Mean by a Fake Ladybird Diamond

Rolex used the Ladybird name for small ladies' Oyster Perpetual watches, and those cases were often factory-set with tiny brilliants or single-cut diamonds. When a replica of that watch sparkles, the question is what the stones are. "Fake" here covers three separate situations: a simulant that only resembles diamond (cubic zirconia, glass, synthetic moissanite), a lab-grown diamond that is chemically diamond but was not mined, and a stone that is misdescribed, such as treated material sold as untreated. Each has its own test path and its own resale outcome. The FTC Jewelry Guides exist because those categories cannot be blended in advertising.

Cubic Zirconia: The Most Common Stone in a Replica Ladybird

  • Pros: inexpensive, bright, cut in the small round sizes a Ladybird bezel or dial needs, and convincing at arm's length.
  • Pros: no thermal signature, so a diamond tester gives a clean no-diamond reading rather than a confusing one.
  • Cons: softer surface, so facet edges round off and scuff within months of daily wear.
  • Cons: higher dispersion than diamond, which gives a noticeably orange or rainbow flash under store lighting.

Under a loupe, look at the facet junctions and the girdle. Worn, slightly rounded edges on a watch that is only a few years old point to CZ, and a refractometer reading near 2.15 confirms it. Use case: fine if you want the look and never plan to resell the watch. Not fine if you are paying a diamond premium.

Glass and Paste: The Stones That Fool Nobody Twice

  • Pros: cheapest option, and soft enough that it never damages the case.
  • Cons: scratches with a fingernail, clouds over time, and shows bubbles or swirl marks that a loupe reveals instantly.
  • Cons: refractive index under 1.8, so it fails a refractometer test outright.

Glass is the material to expect on low-cost replica Ladybird watches with a full diamond-look bezel. Recommendation: treat any such watch as costume jewelry and price it that way.

Synthetic Moissanite: The Stone That Beats Older Testers

  • Pros: hardness around 9.25, so it holds up to daily wear far better than CZ or glass.
  • Pros: high refractive index gives real fire that photographs well.
  • Cons: moissanite conducts heat, so older thermal testers can read it as diamond.
  • Cons: it is doubly refractive, so a loupe can show doubled facet edges and a refractometer gives two readings.

If a tester says diamond but the price says otherwise, ask for a moissanite or multi-tester check. That single step resolves most disputes on vintage-style Ladybird replicas.

Lab-Grown Diamond: Real Diamond, Wrong Label

  • Pros: identical hardness and optics to mined diamond, and it passes every handheld tester.
  • Cons: only a gem lab can separate it from mined diamond with confidence, using screening instruments and spectroscopy.
  • Cons: resale value sits well below mined diamond, so the mislabeling matters financially.

Recommendation: if a watch tests as diamond, get a written lab opinion before treating the stones as mined. This is the one case where a loupe and a tester are not enough.

How to Test Without Damaging the Setting

  1. Inspect all stones at 10x with a loupe, checking facet edges, girdle wear, and inclusions.
  2. Touch the tester probe to the table of each stone, not the prongs, and keep the probe steady.
  3. Use a refractometer on any loose or larger stone for a refractive index reading.
  4. Send the piece to a gem lab when the results conflict or the value is high.

Small melee stones in a Ladybird bezel are hard to test one by one, so test four or five spread around the setting and treat the group as representative.

What the Metal and Setting Tell You

Stamped hallmarks, prong shape, and the evenness of the setting often reveal more than the stones. Diamonds are usually set in gold or platinum with tidy, uniform prongs, because a bench jeweler charges by the hour. Mass-produced replicas tend to use plated base metal, glue, or thick, uneven prongs that sit over the stone. If the setting looks like a casting rather than hand work, assume a simulant until a test says otherwise.

Bottom Line

Assume simulant until a loupe and a tester say otherwise, expect CZ or glass in most replica Ladybird watches, and reserve lab testing for stones that pass as diamond. That sequence protects your money without risking the stones.