Assay: The Guarantee Seal on Gold and Silver Jewelry

When we think about valuable jewelry, such as gold or silver pieces, it is essential to ensure that the material is authentic and of high quality. And that's where assaying comes in — an essential and ancestral practice that protects consumers and truly values ​​each piece.
In this article, we will delve deep into the world of assaying, understand how it works, its importance and history, and even how to identify assayed pieces.
Ready? Let's get started!

What is Assay?

Assaying is the process of verifying, certifying and marking precious metals, such as gold, silver, platinum or palladium. This process ensures that the pieces have the declared purity and that they meet all legal requirements for quality and authenticity.
After certification, the piece is marked with official symbols — called hallmarks — that attest to its composition and purity. These hallmarks are true “visible certificates” printed directly on the jewel or artifact.

Did you know that…some antique pieces bear hallmarks from past reigns?
Has the eagle hallmark (silver) changed design over the centuries?
Does the assay office also cover decorative items, such as cutlery or art objects?

History of Assay Office

The practice of assaying is as old as the use of precious metals itself.

• Antiquity: Historical records show that in ancient Rome and Egypt there were already metal authentication marks.
• Middle Ages: As trade expanded, the need to certify the value of metals became even more important.
• Portugal: In Portuguese territory, assaying has been a regulated practice since the 13th century, gaining formal importance with the establishment of the Casa da Moeda.

Today, certification is carried out by the National Press-Casa da Moeda (INCM).
Portugal is, in fact, one of the European countries with the oldest and most respected assay office tradition.

How does the Assay Office work?

Part Evaluation
Precious metal pieces undergo chemical and physical evaluation to determine their exact composition.

Purity Tests
Purity is tested in the laboratory using specific techniques such as:

• Touch tests;
• Spectrometry analysis;
• Cupellation tests.

Marking
Once authenticity has been proven, the piece is marked with:

• Metal punching (e.g. gold, silver);
• Hallmark/purity (e.g. 925 for silver, 800, 916 or 999 for gold);
• Responsibility mark (identification of the manufacturer or seller). 

Types of Punctures

Each precious metal has its own set of official hallmarks. Let's see some examples:

Additionally, the responsibility stamp identifies the registered manufacturer or seller.

The Importance of Assay

Consumer Protection
The assay office guarantees security for those who buy precious metals, preventing fraud or misleading sales.

Valuing the Piece
A hallmarked piece has more value on the market, whether for sale, exchange or inheritance.

Credibility for Jewelers and Jewelers
Companies that sell hallmarked pieces demonstrate their commitment to quality and transparency.

Responsibility and Rarity of the Piece

Responsibility
The responsibility mark identifies the author of the piece — whether the manufacturer or the trader.
This punch is essential because:

• Allows you to track the origin of the jewel;
• Gives the buyer greater confidence;
• It is mandatory in Portugal and regulated by INCM.

Assay
The assay office process is mandatory by law for all pieces above a certain weight (e.g.: gold pieces above 2g or silver above 2g).
The official hallmark proves that the piece has been duly checked by an authorized entity.

Rarity of the Piece
Antique pieces with historical hallmarks can be considered rare.

• An old punch can indicate a piece of great historical value;
• Rarity can significantly increase market value.

How to Identify Hallmarked Pieces?

• Look for the punctures (usually discreet but visible);
• Verify authenticity using magnifying glasses or photographs;
• Consult official puncture tables;
• Authenticate at a licensed Assay Office, such as INCM in Portugal.

Lusijoia Tip: Quality modern jewelry usually comes with a certificate that includes reference to the hallmarks applied.

Conclusion

Assaying is not just a formality — it is a fundamental practice to protect the value, history and authenticity of jewelry and artifacts made of precious metals.
Whether you are buying, selling or inheriting, understanding the importance of hallmarks and certification is essential.
Only trust certified entities and proudly preserve your hallmarked pieces: they are symbols of tradition, trust and timeless value.

Because every piece of jewelry has a story, and every punch is its seal of authenticity.

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