Ferrea to Speedmaster exhaust valve test

The Ferrea valves may be higher quality I would imagine.
Who here knows definitively? Who has done metallurgical analysis of either brand? And, is it a proven fact that Ferrea actually manufactures and machines their valves? Where’s the stainless sourced from? Lots of companies (in general) import and machine (or finish) as we all know.
Maybe Ferrea does it all, or maybe just machines a nice finished imported valve?