Della and Anne - many thanks for pointing that out. I've been chewing it over, and I can see exactly what you are saying. It's possible that it is just a quirk of the pattern that gives that impression. There is an incut ridge that encircles the pattern, both above and below the "leaf" motifs. It does give the impression that it is a groove that something might fit into / onto. But I wonder if it is just a quirk of the pattern.
I haven't seen anything similar in Brockwitz catalogues (maybe I need to pore over them again though, as I wasn't looking for this shape in the past). Brockwitz certainly did team up metal work with glassware sometimes - they used metal tops on some flower bowls - so I suppose a metal base / holder is a possibility.
It occurred to me that if the piece had a handle, it would be a large basket. That outward flare and the oval shape, coupled with the narrow base are very much like the basket shape.
I was hoping that Pamela might have seen something similar to this shape. If you read this, Pamela, have you seen either this shape before (as big as this) and / or have you seen many examples of Brockwitz Bremen.
And again, thank you Della, and thank you Anne.
Glen