I can say quite categorically that NOT all pieces of Keith Murray glass were marked with the facsimalie mark - despite the fact that it is written in a number of places to the contrary.
I sold a number of pieces to Micheal Parkington for his collection, many of which were unmarked, some of which were in the Exhibition referred to above. You will not find any references to these in the Christies sales catalogues, since all the Keith Murray, along with more than 500 other items of glass, was left to Broadfield house Glass Museum by Micheal's wife, Peggy, when she died.
Interestingly, there is currently another thread about a piece of glass marked 'Asprey', with a registration mark. Unlike that situation, where the shop, Asprey, required there own mark to be put on by the manufacturer, on many other occasions shops (like Liberty's) specifically asked for the manufacturer to leave any identifying marks OFF. This most certainly applies to Keith Murray's work. I currently have some 20 or so pieces of researched and identified Murray that all have pattern numbers fully attributed to them - only 2 have an acid ecthed mark.
Now to the piece in question. Many factories used the bucket/beaker/tumbler form, so that is not something that can be used as a pointer to Murray specifically. In my opinion the pattern of cutting is not synonimous with any of the styles of cutting that can be readily associated with Keith Murray.
To me the pattern appears more likely to be by Webb & Corbett or Thomas Webb & Sons. However, I must stress that is an opinion based purely on gut instinct.
Frank is right that many pieces by Webb seem not to be marked, however this can be true of other factories too, for instance S&W and indeed Webb & Corbett to a lesser degree.
Unlike Frank, pretty well all Rembrandt Guild pieces that I have seen have been marked.