Thanks everyone. I initially thought it was possibly ribbed but it is definitely spiralled. Thanks for the comment on the "moire" effect David, very true. I cannot easily photograph the rim immediately but the raised threading seems near completely melted in near the rim. The jug is about 12cm maximum height. A fair bit of wear, weight and finish make me think Stourbridge. The photo of the vase with applied foot, similar to the jug, I mentioned earlier, as shown in the book by Charles Hadjamach seems to show similar tighter threading than shown on the other pieces in the same image, which are more conventionally threaded. The threading on that piece does not reach the rim though.... Perhaps this jug is a ribbed piece but it seemed plausible it could be a later development of machined threading. As different factories experimented, results could have varied. I appreciate the discussion of cream, creamer and whisky water jugs too..... Any photos or links to pieces with similar decor would be welcome,
Robert (bOBA)