The Lake Governor
I'm pretty sure that you're wrong on this one.There isn't a treatment for a trowel to retain its shape. It can be forced into a certain direction as we can see with one style, however, it can still go the other way in some cases.
I'm struggling to get my point across here I think.
It is Pre-worn, not bent. Majority of trowels on the market are offered as pre-worn, or good to use out the box, in reality, every single one requires more breaking in order to get to its preferred condition - alot of this is down to the plasterer. Everyone applies different forces or pressures, or has different techniques - your trowel wont be the same as someone else's for example. Thats exactly my take on a Permashape. It is force fed into a direction to prevent it going the wrong way. If you get 10 x 14" side by side, the 'bend' will be different on everyone of them. At least with the NELA you create the shape required through use - many are using it directly out of the box, without any issues.
The first pre-worn trowel I ever bought was a Tyzak. Useable straight away but over time curled more, just like any previous stainless steel trowel I'd owned.
Permashape trowels have the corners slightly turned up, just like a naturally worn in stainless steel trowel, but they retain this shape virtually unchanged during their usable lifetime. I'm pretty sure that MT state that the steel has been treated some way to achieve this.