In the title above can someone explain what is meant by “Extreme” in the gun description ??
Is this something Sig actually produced or some modification done by an owner ??

It's a marketing term. I had the exact gun a few years ago and it is a great pistol no matter what they call it.

I picked up the 9mm version - love it. I liked the grips so much, I bought a matching set for my p229. I am learning I don’t like 3-dot sights, though, so Ameriglo I-dots go on.