Over the years I have had a number of items with this technique. I still have a couple in store in crates that contain other items of Thomas Webb. NOT because I know that they are by Webb, rather that I have always associated them with that company, by style and quality, etc..
To date there has been no 'official' recognition through information published, or through my own research. Although to be fair I haven't done as much on them as other factories.
Nigel