Slack (p108) says there is no evidence that these are Sowerby (the colours are wrong) but that Edward Moore is likely as they are colours patented by Edward Moore
I think I've found the source of the Sowerby attribution. Barbara Morris states that: "a vase in this design was bought by the Museum of Decorative Arts in Prague direct from Sowerby & Co. in 1868." How true this is I've no idea but it's an interesting avenue to investigate. it could well be that this was a mix-up but then again there's always the possibility that the Sowerby attribution is correct or that the pattern was made by both firms.
Reference: Morris, B. 1978 Victorian Table Glass and Ornaments
London: Barrie and Jenkins
Lattimore shows this design (in blue and black marbled glass) unattributed along with two other possibly related vases with similar neoclassical motifs.