... I suppose it's a bit like glass and metalwork from the same mould. See here for an example of a glass item made with an officially metalwork mould:
Kevin â€” without other evidence, that's only a possibility. A registration could have been for just one design or decorative feature, for example, initially planned only in metal, but made in other materials later. And other possibilities are known. I think that there's a glass (III) lozenge punched into the metalwork of an early Walsh epergne.
A further possibility is an error, often found on registration lozenges, although more usually of the transposition type when working on a mirror image such as "71" for "17". A final possibility is a simple communications error between management and the mouldmaker â€” they forgot to tell him to use a "III" in the handle, so he used the "I" that he was more familiar with.
If I had all the glass that has passed through my hands here, I would be able to show you just about every error or peculiarity you could dream up â€” and some you would have never imagined!
... I wonder if it could be French, Arcoroc perhaps? ...
TC â€” I was thinking the same, but couldn't remember the brand name!