Coin Pinger
Acoustic bullion authentication — free, private, on-device
Fractional sizes
Fractional coin ping testing — 1/2, 1/4 & 1/10 oz
Fractional bullion carries higher premiums and higher counterfeiting rates per ounce than full-size coins — and a different ring. A smaller disc rings higher (frequency scales with thickness ÷ diameter²), so fractionals ping in the 5–17 kHz range and keep fewer vibration modes under the 20 kHz phone-mic ceiling. Coins under 25 mm are testable but sit at the edge of reliable capture: tap close to the mic, expect retries, and lean harder on the weight and diameter checks.
20 gold fractionals
| Coin | Weight | Diameter | Fineness | c0d2 ring | |
|---|---|---|---|---|---|
| Gold American Eagle 1/10 oz | 3.393 g | 16.5 mm | .9167 gold | 6.68–7.72 kHz | |
| Gold American Eagle 1/2 oz | 16.966 g | 27 mm | .9167 gold | 4.66–5.38 kHz | |
| Gold American Eagle 1/4 oz | 8.483 g | 22 mm | .9167 gold | 5.28–6.11 kHz | |
| Gold APMEX Round 1/4 oz | 7.776 g | 21.7 mm | .9999 | 4.22–5.07 kHz | |
| Gold Britannia 1/10 oz | 3.13 g | 16.5 mm | .9999 | 5.09–6.10 kHz | |
| Gold Britannia 1/2 oz | 15.6 g | 27 mm | .9999 | 3.54–4.24 kHz | |
| Gold Britannia 1/4 oz | 7.78 g | 22 mm | .9999 | 4.00–4.80 kHz | |
| Gold Kangaroo 1/10 oz | 3.111 g | 16.6 mm | .9999 | 4.85–6.00 kHz | |
| Gold Kangaroo 1/2 oz | 15.552 g | 25.6 mm | .9999 | 4.29–5.30 kHz | |
| Gold Kangaroo 1/4 oz | 7.777 g | 20.6 mm | .9999 | 5.11–6.33 kHz | |
| Gold Krugerrand 1/10 oz | 3.393 g | 16.55 mm | .9167 gold | 6.60–7.63 kHz | |
| Gold Krugerrand 1/2 oz | 16.965 g | 27.07 mm | .9167 gold | 4.62–5.32 kHz | |
| Gold Krugerrand 1/4 oz | 8.482 g | 22.06 mm | .9167 gold | 5.23–6.04 kHz | |
| Gold Libertad 1/2 oz | 15.552 g | 29 mm | .999 | 2.65–3.18 kHz | |
| Gold Maple Leaf 1/10 oz | 3.11 g | 16 mm | .9999 | 5.71–6.86 kHz | |
| Gold Maple Leaf 1/2 oz | 15.552 g | 25 mm | .9999 | 4.79–5.76 kHz | |
| Gold Maple Leaf 1/4 oz | 7.776 g | 20 mm | .9999 | 5.85–7.03 kHz | |
| Gold Philharmonic 1/10 oz | 3.121 g | 16 mm | .9999 | 5.74–6.88 kHz | |
| Gold Philharmonic 1/2 oz | 15.552 g | 28 mm | .9999 | 3.05–3.65 kHz | |
| Gold Philharmonic 1/4 oz | 7.78 g | 22 mm | .9999 | 4.00–4.80 kHz |
2 silver fractionals
| Coin | Weight | Diameter | Fineness | c0d2 ring | |
|---|---|---|---|---|---|
| Silver Britannia 1/2 oz | 15.552 g | 27 mm | .999 | 8.98–10.23 kHz | |
| Silver Britannia 1/4 oz | 7.776 g | 22 mm | .999 | 10.19–11.60 kHz |
Small silver rings especially high — the fractional Britannias keep only their fundamental mode under 20 kHz, so they are single-peak references.
Every frequency is computed from first-principles free-plate physics using the mint's published mass and diameter — see the methodology. Each coin's page lists all vibration modes, tolerances, and a physics explainer.
Coin not listed?
Compute the expected ring for any coin from its mass, diameter, and metal with the resonance calculator — or calibrate your own genuine coin directly in the app.