Coin Authenticity & Specific Gravity Wizard
STEP 1 OF 3: SELECT METAL CATEGORY
Which coin category are you testing?
Select a numismatic metal group to load official mint tolerances, or enter custom specifications from any world coin.
Select a Reference Coin Standard
Tap a standard world coin below to load its official mint weight, diameter, thickness, and alloy density.
Enter Official Catalog Specifications
Enter the official catalog weight and alloy composition of the coin you want to authenticate.
Enter Your Physical Coin Measurements
Intrinsic Melt Value & Scenario Simulator
World Coin Alloy Specific Gravity & Density Chart
Specific gravity measures the ratio of a coin's density to pure water (1,00 g/cm³). Because counterfeiters cannot replicate both the exact dimensions and mass of silver or gold using base metals like cupronickel or brass, specific gravity testing remains one of the most reliable non-destructive authentication methods in numismatics.
| Coin Alloy / Standard | Metallic Composition | Millesimal Fineness | Specific Gravity (g/cm³) |
|---|---|---|---|
| .999 Fine Silver (Bullion) | 99.9% Pure Silver | 0,999 | 10,49 g/cm³ |
| .925 Sterling Silver | 92.5% Silver, 7.5% Copper | 0,925 | 10,40 g/cm³ |
| .900 Standard Coin Silver | 90% Silver, 10% Copper | 0,900 | 10,34 g/cm³ |
| .835 Continental LMU Silver | 83.5% Silver, 16.5% Copper | 0,835 | 10,22 g/cm³ |
| .833 Thaler Silver | 83.3% Silver, 16.7% Copper | 0,833 | 10,19 g/cm³ |
| .800 World Circulation Silver | 80% Silver, 20% Copper | 0,800 | 10,15 g/cm³ |
| .750 Commonwealth & Philippine Silver | 75% Silver, 25% Copper | 0,750 | 10,08 g/cm³ |
| .720 Dutch & Mexican Silver | 72% Silver, 28% Copper | 0,720 | 10,02 g/cm³ |
| .500 Half-Silver Alloy | 50% Silver, 50% Cu-Ni-Zn | 0,500 | 9,65 g/cm³ |
| .9999 Fine Gold (24 Karat) | 99.99% Pure Gold | 1,000 | 19,32 g/cm³ |
| .986 Ducat Gold (23.6 Karat) | 98.6% Gold, 1.4% Copper | 0,986 | 18,85 g/cm³ |
| .917 Crown Gold (22 Karat) | 91.67% Gold, 8.33% Copper/Silver | 0,917 | 17,56 g/cm³ |
| .900 Monetary Gold (21.6 Karat) | 90% Gold, 10% Copper | 0,900 | 17,16 g/cm³ |
| Bi-Metallic: CuNi Ring / Brass Core | CuNi Outer Ring + 3-Layer Nickel-Brass Core (e.g. 2 Euro, £1) | Base Alloy | 8,65 g/cm³ |
| Bi-Metallic: Brass Ring / CuNi Core | Nickel-Brass Outer Ring + CuNi Core (e.g. 1 Euro) | Base Alloy | 8,70 g/cm³ |
| Nordic Gold (Cu89 Al5 Zn5 Sn1) | 89% Cu, 5% Al, 5% Zn, 1% Sn | Base Alloy | 7,85 g/cm³ |
| Cupronickel Clad Copper | 91.67% Copper, 8.33% Nickel | Base Alloy | 8,92 g/cm³ |
| Standard Cupronickel (75% Cu, 25% Ni) | 75% Copper, 25% Nickel | Base Alloy | 8,94 g/cm³ |
| Classic Coinage Bronze (95% Cu) | 95% Copper, 5% Tin/Zinc | Base Alloy | 8,80 g/cm³ |
| Nickel Silver / CuNiZn (Cu70 Zn18 Ni12) | 70% Copper, 18% Zinc, 12% Nickel | Base Alloy | 8,70 g/cm³ |
| Magnetic Nickel-Plated Steel (NGC) | 94% Steel Core, 6% Nickel Plating (Magnetic) | Base Alloy | 7,87 g/cm³ |
Frequently Asked Questions About Coin Authentication
How do I perform a Specific Gravity water test on a coin?
Weigh the dry coin in grams on a 0,01 g digital scale (Wair). Next, place a small cup of distilled water on the scale, press Tare to zero it, and suspend the coin completely underwater using a thin nylon thread without touching the bottom or sides. Record the displayed displacement weight (Wdisp) and divide Wair ÷ Wdisp to obtain the exact specific gravity in g/cm³.
How much weight can a genuine silver coin lose from circulation wear?
While uncirculated coins must fall within strict legal mint tolerances (typically ±0,25% to ±0,60%), heavily circulated 19th- and early 20th-century silver crowns, thalers, and Morgan dollars graded Good-4 to Very Good-8 legitimately lose between 1,5% and 3,0% of their original mass through decades of commerce.
Why are caliper measurements critical when testing gold coins?
Modern counterfeiters occasionally use tungsten (19,25 g/cm³) to match the high density of pure 24-karat gold (19,32 g/cm³). However, historic 21,6k (0,900) and 22k (0,917) gold coins such as Sovereigns, Krugerrands, and Double Eagles have a lower density (17,16–17,56 g/cm³), meaning a fake alloy or tungsten core will deviate in thickness or diameter when checked with digital calipers.
How are Actual Silver Weight (ASW) and Actual Gold Weight (AGW) calculated?
Precious metal content is measured in troy ounces (1 troy oz = 31,1034768 grams). Multiply the coin's weight in grams by its millesimal fineness (for example, 26,73 g × 0,900 = 24,057 g of pure silver) and divide by 31,1034768 to get 0,7734 troy oz ASW.