There are lots of tiny balls of silver lined along what would be
the top of the bezel. They look as if they have been pick soldered
there in order to hold the stone in.
I’ve seen this type of mounting once, but didn’t examine it closely.
However, I’d bet it’s made with bead wire. There’s a wire available
in different sizes that looks like a row of beads lined up next to
each other, hence the name. Actually it’s only 1/2, the top half, of
the bead. The bezel may be made from this & then the stone set in the
normal manner (except that the bezel is more difficult to push over).
I don’t know if this type of setting has a special name or not, I’ve
never heard one. A likely name could be ‘bead bezel’ set.