I picked this up last year from someone who had worked for Rosenthal - a very thick-walled vase with an opal core, a layer of clear, applications of light blue and silver nitrate, and cased in another layer of clear. The clear layer between opal and blue gives the vase a subtle 3D effect.
It's marked to the base with acid-etched Rosenthal Studio Linie and facsimile Samuel Herman signature, and engraved pattern number 20427, an unfinished edition number /200 and the word 'muster' - presumably because this would/could have been the archetypal vase subsequent vases were made from.
The person I bought it from thought it was from about 1980, the bits of the internet where Herman/Rosenthal vases pop up claim mid-1970s.
Might anyone have a firmer idea?