Seedplate can be purchased at bitcoinseedbackup.com. It doesn’t appear to make any claims about durability.
As usual, the straight punch method is one I find to be fastest and most user friendly.
Heat Stress Test
As expected, only some discoloration - no data loss.
Corrosion Stress Test
Unaffected by the acid.
Crush Stress Test
Extremely robust; you can see the diamond outline of where I tried to bend it. Even 20 tons of force only managed to deform it a few millimeters.