This one appears in Glen & Stephen Thistlewood's Sowerby - CD catalogue No. 2 - George V to Elizabeth II - and appears on the front cover of the factory Illustrated List No. 35, which they suggest covers the period c. late 1935. Available in sizes of ......... 8.3/4", 5.1/2" and 4.3/4" .... this one is the middle size.
A fairly strong uranium content and definitely an art deco flavour.
I'm not aware of a BoT Rd. No. for this design, though it's possible there is one, but it's unusual for me to search for Sowerby Registrations this late in the factory's history. Sowerby were still being granted Registrations for designs during 1935 which is possibly almost at the end of their activity for this process - looking at the Blue Book they had two Registrations granted during November 1935, though no idea as to what these were.