I can tell you how this piece was made but I have no idea who did it.
This looks to me like about a 4 gather piece. Being that it is not a slumped piece but an offhand blown vase. If I had to guess by the amount of the spread on the white enamel and the amber frit used it was picked up on the 3rd gather and encased.
Blown up to current size, transfered to a punt, then shaped and spun out. You can tell they spun it by the lip collection at the edge of the piece. When they open them with tools the lip is a lot less pronounced or smooth without a ridge.
It also looks like they may have used a kind of drop foot punt to transfer and that would be why you have the donut ring grinding and not your typical punt mark.