From the museum pieces I've taken a good close look at, and the
photos in my reference books (Jewelry: 7000 Years is a great
reference (ISBN 0-8109-8103-3)), there seems to have been two ways
this was done.
Where the pin through the pearl/stone is fixed to the body of the
object, they typically peened the end of the wire into a "rivet"
head, sometime with decorative effects done in the peening process.
All of the ones where the end of the wire is an actual ball, the
other end of the wire is wrapped in to an eye and it's a pendant
attachment to the body of the piece. Often, there is a snippet of
wire soldered on the shaft of the wire to keep the stone in place
(this is how the pearl/bead headed hair and hat pins were done) There
are a number of examples where all they did was loop the end and bend
it down flat to the surface of the pearl/stone.
Remember, most of their hot work was done in air driven charcoal
fires, with a few instances of a blowpipe and candle/oil flame being
used to provide spot heat.
Ron Charlotte -- Gainesville, FL
@Ron_Charlotte1 OR firstname.lastname@example.org