Originally Posted by
goshawkr
Ummm....
There are many alloys of stainless steel, with varying amounts of corrosion resistance. None of them are "junk". There are trade offs in anything. The additive in the alloy that makes SS corrosion resistant also disrupts the magnetic properties of the iron in the steel. So the more the steel responds to a magnet the less it will hold up against rusting. If you need your stuff to resist the highly corrosive environment of salt water, a magnet wont react to it. And yes, there is a point where you can effectively say it is no longer magnetic.
Very few of us are weathering our birds on a salt water beach - so swivels will last a long time even if they are made from a lower grade SS that responds well to a magnet.
Just using a magnet is not diagnostic of what the swivel is made of though. Brass is used in super cheap swivels that are prone to failures, and it is not magnetic either.