thickening was probably not the right word Adam - however, it was the slightly lipped finish to the rim that I was referring to, and having looked again at the 'Fire & Sea' book, can now see that this feature is certainly shown occuring on an Aseda vase (although the vase in question is not the same design as yours). With the Finnish factory, in the same book, I can see only a gradual smooth flare at the rim area. Both of the factories mentioned seem to have used almost identical colours at times, so not so easy to differentiate.
For what it's worth again a comment from the above book..............."In most cases the Riihimaki cased mold-blown pieces are heavier and of finer quality than Aseda."..............presumably you'd need an example from both factories in order to see that difference.