thanks m and Rosie. Does that look like an opaline colour - and is opaline used for pressed pieces? - I really don't know. Pamela has already discussed the Portieux production of these honey pots yesterday, and there is an opaque white Portieux example on the Pressglas-pavillon - also what appears to be a very similar design (on the same site) in clear, from Streit.
However, I'm now being troubled by some additional aspect of Graniver versus Colopal - which in fact Ivo had previously mentioned - but which we seemed eventually to have dismissed. I understand that Colopal is simply an opaque coloured glass, with a surface which is uniformly smooth - whereas Graniver has a variable, slightly pitted and gritty surface texture, and is known to show a mixed marbled/swirled appearance - both effects caused by partially melted distinct, small, granules of glass.
I think that Ivo was correct in his final change of mind to Graniver - based on the quite noticable textured/gritty surface - and it's possible that to date a uranium example of Graniver hasn't been recorded.
I'm led to believe that the names of these two types of glass are derived from: 'COLoured OPALascent', and 'GRANules of VERre'.
I wish to record my sincere thanks to Jay at Hogel and Shoeve in NL for helping me to better understand the difference between these 'types' of glass, and supplying information. I had overlooked to tell Jay that although Ivo had originally suggested Colopal, it was eventually thought that the surface texture made it more possibly Graniver - and there may well be as yet un-recorded colours of Graniver, including uranium.
So - it's likely then that this is Graniver, and my thanks to the experts, as always.