Coin Pinger
Acoustic bullion authentication — free, private, on-device
Constitutional silver
Junk silver ping testing — 90% US coins
"Junk" silver — circulated US .900 coinage from before 1965 — is bought by weight, sold in bulk, and increasingly counterfeited. It ping-tests like any silver disc, with one honest caveat: circulation wear removes mass and softens rims, so genuine specimens ring across a wider band than fresh bullion (our references widen their tolerances accordingly). The good news: the 1965+ clad replacements are copper sandwiches of the same diameter that ring audibly different and duller, so the ping cleanly separates silver from clad. Post-1873 Seated Liberty coins share the Barber planchets below and ring identically.
2 silver dollars
| Coin | Weight | Diameter | Fineness | c0d2 ring | |
|---|---|---|---|---|---|
| Morgan Dollar | 26.73 g | 38.1 mm | .900 silver | 3.86–4.82 kHz | |
| Peace Dollar | 26.73 g | 38.1 mm | .900 silver | 3.86–4.82 kHz |
4 half dollars
| Coin | Weight | Diameter | Fineness | c0d2 ring | |
|---|---|---|---|---|---|
| Barber Half Dollar (1892–1915) | 12.5 g | 30.6 mm | .900 silver | 4.33–5.42 kHz | |
| Franklin Half Dollar | 12.5 g | 30.6 mm | .900 silver | 4.33–5.42 kHz | |
| Kennedy Half Dollar (1964) | 12.5 g | 30.6 mm | .900 silver | 4.33–5.42 kHz | |
| Walking Liberty Half Dollar | 12.5 g | 30.63 mm | .900 silver | 4.32–5.39 kHz |
3 quarters
| Coin | Weight | Diameter | Fineness | c0d2 ring | |
|---|---|---|---|---|---|
| Barber Quarter (1892–1916) | 6.25 g | 24.26 mm | .900 silver | 5.49–6.85 kHz | |
| Standing Liberty Quarter (1916–1930) | 6.25 g | 24.26 mm | .900 silver | 5.49–6.85 kHz | |
| Washington Quarter (1932–1964) | 6.25 g | 24.26 mm | .900 silver | 5.49–6.85 kHz |
Quarters and dimes are under 25 mm — testable, but tap close to the microphone and lean on the weight check (a clad quarter is 5.67 g vs silver's 6.25 g).
3 dimes
| Coin | Weight | Diameter | Fineness | c0d2 ring | |
|---|---|---|---|---|---|
| Barber Dime (1892–1916) | 2.5 g | 17.91 mm | .900 silver | 7.39–9.23 kHz | |
| Mercury Dime (1916–1945) | 2.5 g | 17.91 mm | .900 silver | 7.39–9.23 kHz | |
| Roosevelt Dime (1946–1964) | 2.5 g | 17.91 mm | .900 silver | 7.39–9.23 kHz |
At 17.91 mm the dimes are the smallest coins we reference: high-pitched (~8 kHz fundamental), short, quiet rings at the edge of phone-mic capture. Expect retries.
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.