Coin Pinger
Acoustic bullion authentication — free, private, on-device
Authenticity guide
Is my Mexican 50 Pesos Centenario real?
Four checks — weight, size, magnet, and the ring — catch the overwhelming majority of fakes, because a counterfeit can fake the look but not the physics. Every threshold below is computed from the official spec and our acoustic model.
The 60-second checklist
| Check | Genuine Mexican 50 Pesos Centenario | Red flag |
|---|---|---|
| ⚖ Weight | 41.6666 g ±0.3 g (wear trims a little) | More than ±0.3 g off |
| 📏 Diameter | 37 mm ±0.1 mm | Visibly off, or fails calipers |
| 🧲 Magnet | No attraction at all | Any pull = steel core |
| 🔔 Ring (c0d2) | 3.09–3.90 kHz | Any peak outside the bands below |
What fakes sound like — computed, metal by metal
A struck disc's ring is fixed by √(stiffness ÷ density). A genuine Mexican 50 Pesos Centenario rings its fundamental at 3.09–3.90 kHz (higher modes: 7.17–8.96 / 12.49–15.61 kHz). Here is where the same-size coin lands in the metals counterfeiters actually use — computed from published elastic constants, no guesswork:
| Struck in… | Fundamental | Weight at right size | What you'd hear |
|---|---|---|---|
| Genuine gold | 3.09–3.90 kHz | 41.6666 g | clear, sustained ring |
| tungsten core | ≈7600 Hz | ≈45.3 g | denser than the 22k alloy — a solid replica runs heavy, so real fakes bury a sized tungsten core; the far-higher ring catches either |
| gilded silver | ≈4400 Hz | ≈24.7 g | rings higher and weighs roughly half of genuine |
| gold-plated copper/brass | ≈5950 Hz | ≈21.1 g | much higher ring and badly underweight |
| gilded lead | ≈1950 Hz | ≈26.7 g | a low dead thud, well underweight |
Plated and base-metal fakes also decay faster — solid precious metal has very low internal damping, so a genuine coin ring lasts; fakes die out. Coin Pinger measures both. Full resonance reference →
Known Mexican 50 Pesos Centenario fakes — what's actually out there
The Centenario is one of the most widely counterfeited classic gold coins: the market is full of openly sold gold-plated "replicas" (brass, copper, even lead — common as jewelry) alongside deceptive fakes aimed at buyers that mimic the 41.67 g gross weight. Plated fakes at the correct 37 mm run several grams light, and any magnetic response condemns a piece instantly. The coin predates every modern security feature, so physics carries the load: specific gravity (≈17.4 for the 90% alloy), precise dimensions, and the ring — with professional grading standard advice for any Centenario bought outside a trusted dealer.
Mexican 50 Pesos Centenario authenticity — frequently asked
How can I tell if my Mexican 50 Pesos Centenario is fake?
Run four checks: weight (genuine: 41.6666 g ±0.3 g, a bit less with heavy wear), diameter (37 mm ±0.1 mm), the magnet test (genuine gold is not magnetic), and the ring test — a genuine Mexican 50 Pesos Centenario's fundamental rings at 3.09–3.90 kHz, and every common fake metal rings measurably elsewhere. Passing all four is strong evidence of authenticity; failing any one is a red flag.
Does a fake Mexican 50 Pesos Centenario stick to a magnet?
Only steel-core fakes do — genuine gold is not magnetic, so any magnetic pull means fake. But most fakes (copper-nickel, plated copper, tungsten) are also non-magnetic, so passing the magnet test proves little on its own. Combine it with weight and the ring.
How much does a fake Mexican 50 Pesos Centenario weigh?
Depends on the metal: a tungsten-core fake can weigh almost exactly right (41.6666 g) because tungsten's density matches gold — that's why tungsten fakes fool scales. Gilded-silver or plated-copper fakes of the right size weigh only 24.7–21.1 g vs the genuine 41.6666 g. The ring test catches the tungsten case the scale misses.
Can a counterfeit Mexican 50 Pesos Centenario pass the ping test?
A wrong-metal fake cannot — the ring is set by √(stiffness ÷ density), and no common fake metal matches gold's. The hardest case is a genuine-alloy counterfeit struck to correct specs; those are rare and expensive to make, and against them the ping test is one strong signal among several — combine it with weight, dimensions, and a trusted seller.