Hi, sorry I haven't replied sooner - I've been away trying to sell some plants at the Royal Norfolk Show
I've seen them attributed to Ingrid Glashütte before (never definitive though). They seem to be a common attribution to these bark/ice textured lumps of lead crystal.
Ivo - how would you say the quality of yours compares to Whitefriars? I have never knowingly handled anything from Oberglas (and they don't seem to be in your wonderful little book!).
I will have to keep looking for one with a label...