Hallmark guide
A plain-English guide to the marks found on demi-fine jewellery — what 1/20 12K GF means, how rolled gold differs, and where to look for marks on your pieces.
Quick reference
Markings differ between makers, countries and eras. Treat this table as a guide — each item is confirmed on inspection.
| Mark | Stands for | Construction | What to know |
|---|---|---|---|
| GF | Gold Filled | Karat gold layer bonded to base metal | Often shown with a fraction and karat, e.g. 1/20 12K GF. |
| 1/20 12K GF | 1/20 of the metal weight is 12K gold | Gold filled | One of the most common gold filled marks. |
| 1/20 10K GF | 1/20 of the metal weight is 10K gold | Gold filled | Same layer proportion as 1/20 12K, with a lower-karat layer. |
| 1/10 12K GF | 1/10 of the metal weight is 12K gold | Gold filled | A thicker gold layer than 1/20. |
| RG R.G. | Rolled Gold | Gold sheet bonded to base metal | Common on Australian and British pieces. Layer often thinner than GF. |
| RGP | Rolled Gold Plate | Thinner bonded gold layer | May show fractions such as 1/40. |
| HGP | Heavy Gold Plate | Thicker electroplated layer | No single universal thickness standard; assessed individually. |
Mark by mark
A layer of karat gold is heat- and pressure-bonded to a base metal core. Traditionally, the term “gold filled” has meant the gold layer makes up at least 1/20 of the total metal weight. A fraction such as 1/20 or 1/10 states that proportion, and the karat (10K, 12K, 14K) states the purity of the gold layer itself.
Items marked only “GF” or “14K GF” without a fraction are confirmed on inspection.
Rolled gold uses the same bonding idea as gold filled. The wording is common on Australian, British and European jewellery, lockets, bangles and watch cases. The gold layer is often thinner than gold filled and is not always stated.
Some rolled gold is also marked with a fraction or karat, such as “9ct RG”. Unmarked layer proportions are assessed individually.
Rolled gold plate usually means a thinner bonded gold layer than gold filled. You may see a fraction smaller than 1/20, such as 1/40 or 1/30, next to the mark.
Value depends heavily on the stated fraction and the weight of the item.
HGP (and HGE, heavy gold electroplate) marks describe gold plating that is thicker than standard plating. Plating is electro-deposited rather than mechanically bonded, and there is no single universal thickness standard for HGP.
HGP items are assessed individually, and some may not have enough recoverable gold to make an offer.
Worked examples
A gold filled mark usually has three parts: a fraction (the proportion of the item’s metal weight marked as the gold layer), a karat (the purity of that gold layer) and the construction (GF).
For example, in 1/20 12K GF the gold layer is marked as 1/20 of the metal weight, and that layer is 12 karat gold (50% pure gold). On paper that means pure gold would be roughly 2.5% of the metal weight.
Why the mark isn’t the whole story
Total item weight often includes parts with no gold — springs, clasps, pins, glass, stones and base-metal fittings. Some marks are worn, inaccurate or follow different conventions. Recoverable content can also be lower than the theoretical figure. That’s why each item is confirmed on inspection.
Finding the mark
Marks are often tiny. A magnifying glass, or your phone camera zoomed in, helps — and photos of the mark are very useful to us.
On chains and bracelets, check the flat side of the clasp, the tongue of a box clasp, or a small tag near the clasp.
Open the back of pocket watches and check the inside of the lid. Wristwatch cases are often marked on the case back.
Marks are usually stamped inside the shank, sometimes worn thin from years of wear.
Look on the bail (the loop), the inside rim of the locket, or the back plate.
Check the back plate, the pin stem, near the hinge or on the safety catch.
Usually inside the bangle, near the hinge or on the tongue of the clasp.
Also useful
Some marks indicate standard, thin gold plating. These items usually have very little recoverable gold and may not be eligible for an offer:
Note that a karat on a plated item (for example “18K GP”) describes the plating, not the item.
Watch cases
Older gold filled and rolled gold watch cases were often marked with a guarantee period — such as “Warranted 20 Years” or “Guaranteed 25 Years” — instead of a fraction. These marks generally indicated gold filled construction, but layer thickness varied by maker and era.
Send us a photo. Include a close-up of the mark and a photo of the whole item, and we’ll help you work out what you have.
