You'd be a lot more credible if you knew what you were talking about. A lot of good marine hardware is made of 304 grade stainless steel, which is non-magnetic. The cheaper martenistic grades of stainless steel are magnetic, but the 300 series of austenitic stainless steels are not.
I used to think that too, was taught it fact.
Experience has proven my teachers to be wrong in so many things. - like the idea that the 300 series is all non magnetic... try it, you'll be surprised too.
Like I said, SS is a big subject - but as general rule 316 is the most corosion resistant and the only one I would consider "Marine grade" (even though it will still rust - they all will).
"Good marine hardware made of 304"?
Just last week I had to throw away my boarding ladder - 304 and rusted out from the inside - Couldn't buy one in 316, so had to build one.
"If I knew what I was talking about"... cheap shot - You got shares in a chandlery or something?