Why are some straights magnetized?
They're not heated hot enough. You need to get steel to 1670F to start converting the iron from magnetic ferrite, to the non-magnetic forms of steel.
Heated between 1420F and 1670F it takes on a magnetic structure, but it's not actually magnetic until it cools below 1420F again. Bring it to 1670 and you start developing different structures that aren't magnetic when it cools. At that higher temperature, it gets denser and allows other materials into the structure, and they stay as it cools.
Man, the new avatar threw me off
I noticed my two straights stick to each other by magnetic field. One is a Dovo "special" the other is a Norwood. I did some research and saw some old straights were stamped "magnetized." I was just wondering if this is done intentionally and why.