Hi and welcome to the board. Your potwarmer could be made by one of several makers that we know of, unless it's labelled or matches a known catalogue image we may not be able to pin it down to a maker.
Some of the makers we know of are:
Bel-Mondo
Georgshutte
Huta Szkla Jasle Krosno
La Vide
WMF
POP Glassware Manufacturing Co., Ltd China
Jaslo Poland
Nachtmann
Shenzhen Tea Set Enterprise International company China
We have an album of some of the makers / designs on our GlassGallery here:
http://www.yobunny.org.uk/glassgallery/thumbnails.php?album=990