These Medieval glass beads are found in the UK and Western Europe. The earliest expositions I have seen were presented in Archaeologia ca. 100 years ago. There are also related imperforate objects (that resemble paperweights) that are characterized as "witch stones."

I only know one American private collection that includes them.

In 2006 I showed the beads I documented at the Prehistoric Museum in Munich. I'm attaching my photo/post, about Celtic ring beads.

http://beadcollector.net/cgi-bin/anyboard.cgi?fvp=/openforum/&cmd=iYz&aK=36834&iZz=36834&gV=0&kQz=&aO=1&iWz=0