Guides
Bullion formats and mint specifications guide
Bullion formats guide covering coins, rounds, minted and cast bars, weights, fineness, marks, serials, dimensions, packaging, tolerances, and source scope.
What to take away
- A product specification describes a named product, not every item made from the same metal.
- Gross weight, fine content, fineness, denomination, dimensions, and tolerance answer different questions.
- Coins, rounds, minted bars, and cast bars acquire their shape and markings through different processes.
- A hallmark, serial, assay card, or government denomination is evidence, never a complete authentication result.
- Save the exact source and version used because designs, packaging, and standards change.
Bullion format is the physical and commercial form in which refined precious metal reaches a buyer. Format affects fabrication, markings, package, handling, verification, premium, and resale. A product can contain sound metal while being described under the wrong year, finish, or standard.
Read units first
Precious metals are commonly measured in troy ounces and grams. One troy ounce is about 31.1035 grams, not the 28.35-gram household ounce. Fineness expresses precious metal as a proportion of gross mass.
fine content = gross weight x fineness
NIST Handbook 44's unit tables and device requirements distinguish the 480-grain troy ounce from the 437.5-grain avoirdupois ounce and give their gram equivalents. The handbook governs weighing and measuring devices in its stated scope; it does not certify a bullion product.
Sovereign bullion coins
A sovereign mint issues a coin under legal authority with a denomination, design, and published specification. Bullion, proof, reverse-proof, burnished, and uncirculated versions can differ in manufacture and target market despite equal fine content.
Check year, design, portrait, inscriptions, edge, diameter, gross weight, composition, mint mark, privy mark, and finish. Face value is nominal and should not be used as the metal valuation.
For United States issues the specification is statutory rather than promotional. Section 5112 of title 31, United States Code sets a fifty dollar gold coin at 32.7 millimeters in diameter weighing 33.931 grams and containing one troy ounce of fine gold, a twenty-five dollar gold coin at 27.0 millimeters weighing 16.966 grams and containing one-half troy ounce, and a silver coin at 40.6 millimeters weighing 31.103 grams of .999 fine silver. Gross weight and fine content differ on the gold pieces because the remaining mass is alloy, which is exactly the distinction a specification sheet has to preserve.
Private rounds
A round is a privately made disk without sovereign legal-tender status. It may state maker, weight, fineness, and design. The absence of a denomination does not make it false; the presence of coin-like art does not make it a coin.
Recognition varies. Buyers should obtain the maker's product specification and current resale bids rather than infer quality from appearance.
Minted bars
Minted bars usually begin with rolled metal cut into blanks, then receive precise surfaces and markings. Many retail examples come in sealed, serialized cards. Uniform finish can aid comparison, but the card can be copied or altered.
Record bar and package serials separately. Ask whether the serial is independently searchable, whether the card must remain intact, and which tests can be performed without opening it.
Cast bars
Cast bars form when molten metal is poured into a mold. Cooling can create flow lines, shrinkage, rounded edges, or dimensional variation. Judge them by the producer's published limits and appropriate examination, not the mirror finish expected from a minted bar.
Large wholesale bars have their own market standards, approved custody, weighing, and acceptance systems. A small bar from the same refiner is not automatically a wholesale Good Delivery item.
What markings can establish
| Mark | Useful evidence | What it cannot prove alone |
|---|---|---|
| Metal name or symbol | Claimed material | Actual composition |
| Weight | Claimed gross or fine amount | Correct unit or tolerance |
| Fineness | Claimed metal proportion | Uniformity through the item |
| Hallmark | Claimed maker or assayer | Authentic issuer or current status |
| Serial | Item-to-record relationship | Genuine metal or unique use |
| Denomination | Claimed sovereign coin identity | Market value or genuine specimen |
| Assay card | Claimed product and test relationship | Untampered contents |
Authentication comes from agreement across provenance, specifications, markings, measurements, security features, and suitable tests.
Build a specification sheet
For every product, store:
- Official product name and number
- Issuer, refinery, and facility if relevant
- Metal, gross weight, fine content, and fineness
- Dimensions and published tolerances
- Obverse, reverse, edge, and finish
- Hallmark, serial, date, and assay marks
- Original package and certificate
- Effective year or version
- Source URL, access date, and archived copy
Add actual measurements in a separate column. Never overwrite expected values with observed readings.
Common questions
Does 999.9 mean the item weighs 999.9 grams?
No. It normally expresses fineness in parts per thousand. Weight must be stated separately.
Is a round a counterfeit coin?
Not merely because it is round. It becomes deceptive if represented as a sovereign coin or with false metal claims.
Should a cast bar look perfectly smooth?
Not necessarily. Production can leave normal variation. Compare the item with its actual producer specification.
Does a serial number prove ownership?
No. Link it to invoices, custody records, photographs, and transfers to support ownership evidence.
In this guide
- How to read a bullion product specificationBullion specification method covering product identity, year, metal, gross and fine weight, fineness, dimensions, edge, finish, marks, package, and tolerance.
- Sovereign coins, private rounds, cast bars, and minted bars comparedSovereign coins, private rounds, cast bars, and minted bars compared by legal status, manufacture, marks, packaging, premium, inspection, divisibility, and resale.
- Mint, refiner, hallmark, and serial-number checklistBullion hallmark checklist covering issuer identity, refinery location, assay stamps, serial formats, dates, fineness, dimensions, packaging, lists, and records.