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Gold coin guide
German 20 Mark — ping test & specs
The Imperial German 20 Mark (1871–1915) rides its own statutory planchet — 7.965 g of .900 gold at 22.5 mm (2,790 marks to the kilogram of gold) — slightly heavier and wider than the LMU coins, with a distinct ring.
Opens the free tester with this coin preselected — audio never leaves your device.
Official specifications
| Weight | 7.965 g |
| Diameter | 22.5 mm |
| Composition | .900 gold (90%) |
Source: Imperial German mints. Coin Pinger checks measured weight and diameter against these values.
Expected resonance range
Good confidence*| Mode | Expected ring | Recommended variance |
|---|---|---|
| c0d2 | 4.33–5.45 kHz | ±11.5% |
| c0d3 | 10.05–12.55 kHz | ±11.1% |
| c0d4 | 17.58–21.96 kHz | ±11.1% |
A genuine German 20 Mark rings within these ranges at its c0d2/c0d3/c0d4 vibration modes, fixed by its size and metal. The recommended variance is how far a genuine specimen's ring can sit from each center — built up in quadrature from real manufacturing tolerance and temperature (under 1%), phone-mic capture reproducibility (≈4%), an extra allowance on the fundamental for minting-asymmetry splitting, and a per-metal model-uncertainty term (largest for .9999 gold, whose modulus is least certain). This coin's band is widened further because circulated 90%-silver classics lose mass and edge crispness with wear, spreading their ring. The higher modes also carry a small thick-plate centre correction, since a real coin is not infinitely thin. The good-confidence tag reflects how well-established this metal's constants are: Computed from 22k-gold alloy constants, which are slightly less certain than silver; the band is set accordingly. These are guidance bands, not exact values — see the methodology for the exact formula, or calibrate your own coin in the app for a specimen-exact reference and tighten each peak per coin.
Small-coin note: at 22.5 mm this coin is below the ≥25 mm sweet spot — its ring is higher-pitched, shorter, and quieter than a full-size coin's. Tap close to the microphone in a quiet room, expect more retries, and lean harder on the weight and diameter checks.
* These are computed guidance ranges. Certain your German 20 Mark is genuine but it won't match? Send us its ring — we'll dig in and improve the reference.
🎙 Submit sample pingsHow to ping test a German 20 Mark
- Hold — grip the coin by its center (a nodal point) in a coin ping-test holder so the rim rings freely; a fingertip at the center is a last resort.
- Tap — strike the edge with a striker near the microphone.
- Read the verdict — MATCH or NO MATCH against the peaks above, plus weight and size checks.
German 20 Mark — frequently asked
How much does a German 20 Mark weigh?
The official specification is 7.965 g in .900 gold (90%) (source: Imperial German mints). Coin Pinger's weight check allows ±0.3 g by default. Circulated specimens lose a little mass to wear, so weigh toward the low side of that window.
What size is a German 20 Mark?
22.5 mm in diameter, per Imperial German mints. Note the average disc thickness is less than the rim caliper reading — the raised rim and relief concentrate metal at the edge.
What frequency does a genuine German 20 Mark ring at?
Its fundamental (c0d2) vibration mode is computed to ring in the 4.33–5.45 kHz range, with higher modes near 10.05–12.55 kHz and 17.58–21.96 kHz. These are first-principles physics computations from the coin's published mass, diameter, and metal — not measurements of sample coins.
Why does my genuine German 20 Mark ring slightly off the listed frequencies?
Wear is the biggest factor for the German 20 Mark: circulated 90%-silver classics lose mass and edge crispness, which spreads the ring across specimens. On top of that, phone-mic capture moves a genuine peak a few percent tap-to-tap (strike point, how you hold it, the mic itself). That's why this reference band is wider than a modern bullion coin's.
Does ping testing damage a German 20 Mark?
No — the test needs only a light tap on the edge with a non-marring striker (a wooden pencil or plastic stylus works well), far gentler than normal handling. Hold the coin at its center so the rim can ring freely.