Hello,
Given the information that Chris has added about his visit to the Red House Cone I guess I've got to be a bit cautious. I am always happy to learn.
An observation that I have is that Stuart prided themselves in marking all their production - as claimed in adverts and other publicity material. Of course this was not always the case. For instance if items that were made especially for a particular retailer who stipulated that they were not marked, or else (presumably) if they were seconds.
Unless all the tankards were made for one retailerr (which of course is possible) I would have expected that by now one of us would have unearthed one marked "Stuart".
On the other hand Webb is often found unmarked and has given attribution problems over the years for that very reason.
Not by any means conclusive, but at least a valid point within this discussion.
I notice my comments, in the other thread linked, stated that I cannot recall seeing a marked version, so your points are indeed important Chris.
Nigel