These jugs have been discussed on a number of occasions on the GMB. There is no conclusion, since none have been found marked, or labeled. Nor have they been seen in archives as yet,........but then nobody has been looking specificlly for them

Possibly Webb, or Stevens & Williams, but no assurances there. However, they are not Whitefriars, since there are too many inconcruities in their characteristics.
Nigel