1. Jewelry Identifier
  2. Hallmarks
  3. SHIBUICHI

* mixed-metal hallmark

The SHIBUICHI hallmark: meaning, purity & value

Japanese copper-silver alloy (typically 75% Cu / 25% Ag, hence the name 'one fourth'). Develops grayish patina; used in mokume-gane layering and standalone pieces.

Published May 30, 2026

Quick facts

Metal
mixed-metal
Common regions
Japan

Stamps that mean the same thing

This purity may be struck into jewelry as any of: SHIBUICHI / 四分一. The mark differs by country and era, but the metal content is identical.

What SHIBUICHI tells you

Japanese copper-silver alloy (typically 75% Cu / 25% Ag, hence the name 'one fourth'). Develops grayish patina; used in mokume-gane layering and standalone pieces.

How to check it yourself

  1. Examine the stamp under a 10× loupe — genuine marks are crisp and evenly struck, not doubled or smeared.
  2. Confirm the mark reads SHIBUICHI or an equivalent such as 四分一.
  3. Photograph it in the Jewelry Identifier app to read the metal, hallmark, and any gemstones from the image.
  4. For a binding result, have an assay office or gemological lab run an XRF purity test.

* Frequently asked

FAQ

Q. Is SHIBUICHI the same as 四分一?
A. Yes. SHIBUICHI, 四分一 all denote the same material — mixed-metal. Different markets and eras stamp it differently, but the purity is identical.
Q. How do I confirm a SHIBUICHI stamp is genuine?
A. Look at the mark under 10× magnification for crisp, even strikes, cross-check the weight-to-volume ratio against the expected density, scan it with the Jewelry Identifier app, and — when it matters — have an XRF test done by an assay office or gemological lab.

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