Lead can be present in most if not all older alloys (including gold!), as people in ye olden days simply didn’t know how dangerous it was. Old paste jewellery will also contain lead (just like lead crystal glasses). That being said, smaller amounts of lead, cadmium or other heavy metals in a piece of antique jewellery that is worn occasionally probably poses a very limited threat to your health. It is also quite likely that whatever lead that may leach out has already done so, due to contact with the former owners’ skin through the past 100+ years; contact with an acidic surface is known to make lead leach out (which is why you shouldn’t serve orange juice from lead crystal), and while our skin isn’t as sour as OJ (3.9), it’s on the acidic side (between 4.5 and 6).

On a general note, I would therefore advise against wearing any piece of jewellery that you suspect may contain lead or arsenic on a daily basis, and make sure you don’t put it in your mouth (if you are so inclined).

Note that lead swab test kits like 3M LeadCheck are available online. They will tell you if there is lead present on the surface, so if the piece is made of the same material all the way through, it will give you a good indication of its safety. However, the piece is a basemetal containing lead plated with a more noble alloy, the test will be negative unless you manage to test a spot where the plating has been rubbed off. In such cases, you may need to scratch the metal, but this will of course damage the piece.

There are test kits available for other heavy metals, but please make sure that you get one that is actually suitable for metals, and not a test for tap water or urine samples. These tests will usually require you to scrape off a bit of the metal and convert the particles into a liquid solution, so again, you will have to damage your antique pieces.