Those are not "OPEN MODEL HEADS". Miura forges their own heads.
Kyoei forges Vega as their own line and KZG also comes out of their foundry along with a few other small brands.
The Endo foundry produces Epon heads and I've just learned that they also make heads for Mizuno.
I have hit Mizuno, Miura, Vega and Epon and I can tell you that each brand has a distinctly different feel. I have not hit Scratch irons yet.
I'm pretty sure this info is correct. If not please correct me.