Grading and Authenticating Ancient Japanese Cast Coins

Ancient cast coins cannot be assessed by transferring strike-coin grading rules unchanged. Original casting weakness, later circulation, burial corrosion, cleaning, tooling, and modern replication leave different evidence and should be recorded in separate fields.

表Exact primary face unavailable 裏Exact other face unavailable

Method: Cast-coin specific
Core split: Manufacture / wear / corrosion
Authentication: Evidence, not photo verdicts
Status: Educational guide

Condition recording

Grade what is present, and name the cause carefully

Inscription completeness

Record each legible character and whether weakness is cast, worn, corroded, or uncertain.

Outer rim and inner rim

Note completeness, weakness, breaks, clipping, and later filing separately.

Square hole

Record shape, casting roughness, filing, distortion, cracks, and later enlargement.

Surface

Separate stable patina from active corrosion, encrustation, pitting, harsh cleaning, and applied color.

Fabric and casting

Record porosity, metal flow, weak areas, seams, sprue remnants, and edge finishing without assuming every irregularity is damage.

Authentication

Modern copies leave combined evidence

No single diameter, color, seam, or character proves authenticity. Evaluate the complete evidence set and provenance.

Calligraphy

Compare all characters and spacing with documented examples; incorrect forms or copied flaws can be diagnostic.

Size, weight, and metal

Use source ranges as comparative observations, never as a single pass/fail cutoff. Corrosion and damage change measurements.

Mold repetition

Exact repeated pits, scratches, or edge defects across supposed ancient pieces may reveal transfer molding or modern copies.

Patina and deposits

Artificially uniform color, deposits that ignore recess geometry, chemical odor, or fresh metal under false crust require specialist review.

Provenance and expertise

A photograph cannot establish authenticity. Preserve collection history, measurements, material analysis, and specialist opinions.

Not an authentication service

WorldCoinBook records educational diagnostics. A photograph cannot establish authenticity, grade, metal, or market value.

Evidence

Sources and scope

These links support the claims on this page. Source authority does not imply permission to republish source images.

Wado Kaichin Research Catalog and Measurement Guide Currency Museum, Bank of Japan

Wado Kaichin specimen classification, calligraphic distinctions, measurement method, diameter, and weight evidence.

Open source

Measurement Catalog for Ancient Coin Types from Mannen Tsuho through Kengen Taiho Currency Museum, Bank of Japan

Specimen-level outer diameter and weight observations for issues two through twelve; observations are not statutory standards.

Open source

Chemical Composition Study of the Twelve Ancient Coin Types Institute for Monetary and Economic Studies, Bank of Japan

Measured copper, tin, lead, iron, arsenic, and antimony patterns across sampled ancient coins, with specimen-level limitations.

Open source

Asukaike Site Heritage Record Nara National Research Institute for Cultural Properties

Asukaike production complex, Fuhonsen, molds, casting debris, crucibles, files, and court-workshop archaeological context.

Open source