Multiple angle seats are ground with stones. Radiused seats are machined with a machining center like a Serdi. Here is a diagram of a Serdi carbide cutter. View attachment 1716264482
Yup, I’m aware of the options but am curious what was used. I’ve heard that the shallower angles can be difficult with stones. I’ve got a nice Sioux valve and seat setup but haven’t played with it yet.