I think Bernard is quite right to be sceptical and throw in a word of caution - a man after my own heart, as the saying goes.
It hardly seems necessary to add my 4 penny worth, but I did see this thread originally and assumed it would be sorted out fairly quickly
For as long as I can remember I have thought these to be from Thomas Webb. My reasons are much as has been shown in the photos by other GMB members. I cannot even remember whether or not I've seen a marked version, but IMHO I think much of their work is unmarked. Indeed a few years ago, my partner and I were at a local antique fair where I bought a 1900's green Stuart carafe and she bought a half pint beer mug - unmarked, but sold as 1930's Powell. She uses this Webb tankard for her occasional beer on a regular basis
Oh, dear what have I said??
BTW I have looked up the stylendesign attribution mentioned above - it is only based on the colour, as the glass shown in their reference "The Crystal Years" is a plain, footed piece and not wave-ribbed, like the mugs in question (or indeed the jug they are selling, also wave-ribbed).
Hope that helps, Nigel