Three categories, three very different values, and one small stamp that usually tells you which is which. Gold-filled jewelry contains a real layer of gold bonded to brass and holds its color for decades of daily wear. Plated jewelry carries a flash of gold measured in microns and wears through at the ring band within a year or two. Solid gold is solid gold. Knowing which is in your hand is the difference between paying $18 and $180 for two brooches that look identical.
The marks are regulated, at least in part, and the wear points do not lie. The two tests most people rely on, a magnet and a drop of acid, are the least reliable tools available.
Read the mark first
- 1/20 12K GF
- Gold filled. One twentieth of the total metal weight is 12-karat gold. Under the FTC's Jewelry Guides, gold filled needs a layer of at least 10 karat making up at least 1/20 of the weight.
- 12K GF, 10K GF
- An older gold-filled mark without the fraction. Treat it as gold filled and check the wear points.
- Rolled gold, RGP
- Rolled gold plate, a thinner layer than gold filled. RGP is a plated mark, not a filled one.
- Vermeil
- At least 2.5 microns of gold over sterling silver.
- 585, 750, 375, 14K, 18K
- Solid gold. 585 is 14 karat, 750 is 18 karat, 375 is 9 karat.
At a glance: what the marks mean
The market test, in order
- 1
Find the mark
Inside a ring band, on the tongue of a clasp, on the pin stem of a brooch and on the bail of a pendant. Take a loupe: most of these marks are under a millimeter and worn smooth on older pieces.
- 2
Turn the piece over and look for the wear points
The back of a ring, the clasp tongue, the hinge and the highest points of the design. Green or gray base metal means plating; a continuous line of gold means gold filled.
- 3
Weigh it in your hand
Gold alloy is noticeably denser than brass. A piece that feels light for its size is plated or hollow-formed.
- 4
Bring a magnet, then ignore the result
A magnet will not stick to gold, but it will not stick to brass or copper either. It only filters out nickel, steel and iron. Passing it is not evidence of gold; failing it is.
- 5
Leave the acid at home
Nitric acid destroys plating, reads unreliably on gold-filled surfaces and can damage a signed piece. If something is worth testing, take it to a jeweller with an XRF analyser.
- 6
Price from the mark, not the shine
An unsigned plated brooch is a cheap object however attractive it is. The same design marked 1/20 12K GF is worth more, and in 14 karat gold it is worth its metal weight plus a design premium.
What each check actually tells you
| Check | What it tells you | How far to trust it |
|---|---|---|
| Mark inside the band | Gold filled, plated or solid, if the mark is original | Strong, unless the piece has been re-marked or the mark is a later fake |
| Magnet sticks | Base metal containing iron or nickel | One-directional only: brass and copper pass just as gold does |
| Green or gray metal at the wear point | The gold layer has worn through, so the piece is plated | Strong |
| A continuous gold line at the wear point | Gold filled, with a layer thick enough to survive wear | Strong |
| Nitric acid on the surface | Can confirm solid gold, unreliable on filled pieces | Moderate, and destructive |
What each category is worth
Solid gold is priced on metal. A 14-karat piece is worth its melt value plus whatever the design adds, and a 5-gram ring is a metal trade first and a jewel second.
Gold-filled jewelry is worth a small fraction of its gold content and is priced almost entirely on design and maker. That is not a reason to avoid it: a good 1940s gold-filled brooch is more wearable than most modern plating, its color does not fail, and the supply is fixed. It is a reason not to pay solid-gold prices.
Plated costume jewelry is worth what the design and the signature are worth, and nothing for the metal.
Signed costume jewelry: the numbers
- Miriam Haskell — Hand-strung glass and crystal, 1930s to 1960s, most valuable. Signed necklaces command the highest prices in costume jewelry, and early unsigned pieces are identified by construction. Haskell (1899 to 1981) designed affordable pieces with her partner Frank Hess from 1920 through the 1960s, and her vintage pieces are eagerly collected.
- Eisenberg — The sterling-marked pieces are the ones to look for, which sell for more. The base-metal line is worth much less.
- Trifari — Crown-marked 1930s to 1950s pieces, particularly the Alfred Philippe designs, sell well. Later plain Trifari is much cheaper.
- Weiss, Coro, Napier, Monet — Solid, wearable mid-century costume jewelry, generally affordable when signed. Excellent value for everyday wear.
- 1980s Dior and Chanel costume — Sought after and priced accordingly, though Chanel costume is the most counterfeited in the category.
Five pieces to hunt, and what to pay
Anything unsigned should be bought to wear, at roughly a third of these figures. Prices are shown only where we confirmed them on the brand or retailer page in Oct 2026.
Best hold valueTrifari
Alfred Philippe era brooch, crown mark
The most collectable mid-century American costume maker, and the easiest to authenticate because the crown mark is period-specific. Buy signed, and check for enamel loss.
Search EtsyMiriam Haskell
Signed glass and pearl necklace
Haskell pieces are identified by construction as often as by signature, and early examples carry no mark at all. Look for hand-wired settings and a Russian gold finish.
Search eBay
Eisenberg
Sterling signed brooch
The sterling-marked pieces are a separate market from the base-metal line and are frequently mixed up. Check for the word sterling on the piece itself rather than trusting the listing.
Search Poshmark
Gold filled
1/20 12K GF bangle, 1940s
The best everyday-wear category here: real gold color, thick enough to survive daily use, and priced on design. Ignore any piece showing base metal at the hinge.
Search Depop
Vintage Dior
Costume pearl necklace, signed
A strong wearer with a resale floor, because the name is legible and the buyer pool is large. It is also the most counterfeited corner of costume jewelry, so buy from sellers who show the clasp.
Search Vinted
