eBay

【Product Size】0.47 x 1.57 inches with N40 Neodymium Magnets; Package: 2 pack; Pull Power: Over 2 pounds per magnet, 8 pounds for the pair. This gold testing magnet is the perfect size and strength for identifying fake silver and gold jewelry!
【Jewelry & Coin Testing】Identify fake/plated jewelry, which often has steel or nickel alloys as the base material (some alloys, like nickel-silver and German silver are non-magnetic, despite having ferrous metals present). Generally, the magnet test is only the first test performed when verifying the authenticity of coins and jewelry, before density and acid testing.
【Precious Metals Testing】Identify/sort chrome plated items from polished aluminum, silver, and non-magnetic grades of stainless steel (chrome plating requires a nickel layer, which is magnetic). Identify and sort solid brass and bronze from steel-plated items (handy in the antique market and hardware store).
【Practical Magnetic Keychain】This magnetic keychain is strong, small, light in weight, and easy to carry. You can put it in your pocket or purse when you go out. It provides you with a versatile multi-functional magnetic testing tool.

These keychain magnets offer strong neodymium magnet power in a handy keychain. They are perfect for jewelers, recyclers, coin dealers, or anyone that needs a convenient, easy-to-carry magnet to test for iron, nickel, or cobalt content. Featuring a durable neodymium magnet housed in a metal shell, it holds over 2.5 pounds. Determine if jewelry is silver or gold plated by testing if ferrous metals are used as the base metal (excluding some nickel alloys). If a magnet responds to jewelry, it is not fine silver or anything near pure gold. The same is also true of brass and bronze antiques, many are just brass plating over steel or iron. The magnet can also be used to determine polished aluminum from stainless steel in most cases, and is very handy for testing industrial metals for recycling.Features a powerful N35 grade (1.5 lbs minimum pull strength) neodymium rare earth magnet encased in a plated brass housing for durability and comes with a stainless steel split ring.Product Specifications Type: Neodymium Magnet Keychain Material: N35 Neodymium Dimensions: 0.47 inches wide at its widest point x 1.57 inches long (12 x 40 mm) Net weight 0.6 oz (18 g)