Custom Jewelry Markings & Stamps: What Do They Mean?

Have you always wondered what the markings and stamps on jewelry mean? Or do they look strange to you? To be honest, these markings & stamps can get you confused and make you uninformed on the type of jewelry to buy.

In this guide, we will go into detail on the various jewelry stamps and meanings. We will help you understand the lingo of these markings and how you can use this knowledge when ordering new items.

What Does A Hallmark/Stamp Mean on Jewelry?

Jewelry markings, hallmarks, and stamps are basically a set of letters, numbers, and symbols that represent different features of a jewelry. They are short forms for the material composition of the jewelry, certifying their authenticity and quality. For example, when you see “18K” on gold jewelry, it simply means the jewelry is 18 karat gold.

How to Read Gold Hallmarks on Jewelry?

Jewelry hallmarks are often written as a combination of numbers, letters, & symbols, and they are usually located at the back or interior of the jewelry.

• Hallmarks: These are markings used to identify the country of origin, date, and the type of metal used for the jewelry.
• Purity Stamps: These jewelry stamps indicate the percentage of precious metal in the jewelry. For gold, they are shown as karats (14K) or as a three-digit number (“585” for 14K gold, meaning 58.5% pure gold).
• Brand Logo: These letter markings on gold jewelry are usually the brand’s logo. They serve as trademark stamps to promote the brand’s excellence. An example is the TIFFANY & CO. jewelry collection, which always has “T & CO.”

Jewelry Metal Purity Stamps List

The table below contains different types of metals, their jewelry stamps list, and their percentage of pure metal content:

Metal Type	Stamp	% Pure Metal
Gold	24K, 999	99.9%
Gold	22K, 916	91.6%
Gold	18K, 750	75.0%
Gold	14K, 585	58.5%
Gold	10K, 417	41.7%
Gold	9K, 375	37.5%
Silver	S925/925/.925/STER	92.5%
Silver	S999/FS	99.9%
Platinum	PT999	99.9%
Platinum	PT950	95%
Palladium	PD950	95%
Stainless Steel	S.S. / STAINLESS	Varies

Silver Purity Marks

This section covers the common hallmark stamp on silver:

S925 / 925 / .925 / STER

On jewelry what does 925 mean? S925 / .925 / 925 stamp on jewelry indicates 92.5% pure silver and 7.5 alloyed metals for additional durability. They are commonly called sterling silver jewelry, hence why they sometimes have the STER or SS marking.

S999 / FS

This mark stands for silver items with the highest level of purity. FS means “Fine Silver” and S999 means it contains 99.9% pure silver. Due to the high purity, this silver type is softer and more malleable than sterling silver, making it less common for everyday jewelry. However, they can be used in specialized designs among auctioneers.

Gold Purity Stamps

This section covers the most common gold hallmarks on jewelry:

10 Karat Gold Hallmarks

• Stamp: 10k / 10kt / 417
• Content: 41.7% pure gold + alloy

These jewelry marks on gold indicate 41.7% pure gold while the remaining is a mix of other metals. The mix of metals makes the jewelry more strong and resistant to wear.

14 Karat Gold Hallmarks

• Stamp: 14k / 14kt / 585
• Content: 58.5% pure gold + alloy

The 14 karat gold stamp means that the jewelry is composed of 58.5% pure gold and a mixture of other metals. The added metals further beautify the jewelry and make it more malleable.

18 Karat Gold Hallmarks

• Stamp: 18k / 18kt / 750
• Content: 75.0% pure gold + alloy

18 carat gold hallmark number, which can also be shown as 750 gold means 75% pure gold and 25% of other metals. The larger amount of gold in 18K solid gold jewelry gives it a stronger yellow tone than the lesser karats.

22 Karat Gold Hallmarks

• Stamp: 22k / 22kt / 916
• Content: 91.6% pure gold + alloy

These hallmarks mean that the gold jewelry contains 91.6% pure gold while the remaining is made of alloyed metals. Since it contains a much higher percentage of pure gold, it’s usually very yellow and can be mistaken for 100% pure gold.

24 Karat Gold Hallmarks

• Stamp: 24k / 24kt / 999
• Content: 99.9% pure gold + alloy

These are the highest gold hallmark on jewelry. It means the piece contains 99.9% pure gold. But jewelry pieces are rarely made with this type of gold because they are very soft.

Other Metal Stamps

Platinum

• PT999 / Plat: This indicates 99.9% pure platinum. It’s extremely rare and expensive, typically used for special pieces.
• PT950 / Plat: Contains 95% pure platinum and 5% other metals. It’s the most popular platinum standard for fine jewelry, as it offers excellent durability, hypoallergenic properties, and lustrous white color.
• PT900 / Plat: Composed of 90% platinum and 10% other metals. It’s less expensive than other platinum standards but still considered high-quality.

Palladium

• PD950: Contains 95% palladium with 5% other metals. As part of the Platinum Group Metals (PGMs), this palladium maintains its natural white, hypoallergenic, and light nature.
• PD500: Contains 50% palladium and alloyed with the same percentage of other metals (mostly silver and copper). This lower purity makes it cheaper, but it still maintains its white color and hypoallergenic qualities.

Stainless Steel

• S.S. / STAINLESS: This is a general marking for stainless steel composition. It’s durable, corrosion-resistant, and hypoallergenic, making it good for jewelry that are worn everyday.
• 316L/304: Stainless steel usually has 316L or 304 stamps. 316L is a surgical-grade stainless steel that offers superior corrosion resistance and biocompatibility. 304, on the other hand, is resistant to corrosion but slightly less durable.

Letter Markings on Gold Jewelry: What Do They Mean?

What do the letters on gold jewelry mean? Below is a comprehensive interpretation of common letter markings on gold jewelry:

Letter Marking	Meaning	Description
GF	Gold-Filled	Thick gold layer (at least 5% gold by weight) bonded to base metal; much durable than plating.
HGP / HGE	Heavy Gold Plated / Electroplated	Thicker electroplated gold layer; not solid gold.
GP / GE	Gold Plated / Electroplated	Thin gold coating applied by electroplating.
G / Au	Gold / Aurum	“Au” is the symbol for gold; may appear with purity (e.g., Au750).
Au	Gold (Chemical Symbol)	Indicates gold content, often used with a numeric mark like “Au585” for 14K gold.
KP	Karat Plum	Exact karat purity (e.g., 14KP = true 14K gold).

GF

GF stands for “gold filled,” which is a mark that indicates a thick layer of gold bonded over a base metal. The bonded gold layer must constitute at least 5% of the gold filled jewelry by jewelry weight.

HGP / HE

Stands for “heavy gold plated / heavy gold electroplated.” This marking means the base metal is plated with at least 2.5 microns of gold.

GP / GE

Stands for “gold plated / gold electroplated.” These letter markings mean that the gold that’s plated on the base metal is not more than 2.5 microns. It’s the opposite of HGP / HE.

G / Au

G stands for “Gold” and Au is the chemical symbol for gold. This marking means that the jewelry is made of gold but not 99.9% gold purity level.

KP

Stands for “Karat Plum,” meaning the jewelry is solid gold and ascertains the exact karat as stated. For example, 14KP means the item is made of 58.5% pure gold.

Practical Tips for Jewelry Brands: Know These for Your Custom Jewelry

Are you a jewelry brand owner? After knowing jewelry marking meanings, these are the various ways to apply the knowledge in your brand:

Consider Stamping as Part of Collection Branding

One way to build your brand and look professional is to stamp your collection with your logo. This helps to strengthen your brand identity and make you easily identifiable among competitors. Partner with manufacturers that offer private label jewelry and stamping services.

Use Accurate Purity Stamps Only

Only use jewelry markings and stamps that match the actual material content (e.g., 925 for sterling silver). Ensure strict quality control. Don’t stamp plated pieces with “14K” or “18K” alone – add “GP” or “GF” to avoid misleading consumers and beaching compliance.

Choose Stamping Position Wisely

Plan ahead for where stamps will be placed (whether inner ring band, clasp tag, back of pendant, etc.). A clear yet discreet location preserves the design while ensuring traceability. You can speak with your custom jewelry manufacturer for the right place to place the stamp.

Check Manufacturer’s Qualifications & Jewelry Certification

Before deciding on the manufacturer to work with, check their jewelry certifications, years of experience in the industry, and other qualifications. To ensure authenticity, go further by asking for some certification for gold stamped jewelry.

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