Unfortunately, Roy, there are no simple answers for the pattern number or RD number of this pedestal sugar bowl.
I can’t find a matching Sowerby pattern in any of the extant pattern books.
The registry date lozenge for 6 March 1876 – Parcel 3 covers a bundle of Sowerby design registration numbers 298870 to 298876 inclusive.
Neither Jenny Thompson nor Simon Cottle describe RD 298870.
RD 298871 is described neither by Thompson or Cottle, but is spill holder / posy vase (pattern no 1148).
RD 298872 is described as ‘elaborate sugar’ by Thompson and merely ‘sugar’ by Cottle.
RD 2898873 is described as ‘bowl’ by both.
RD 298874 is described as ‘covered dish’ by both.
RD 298875 is described as a ‘pail’ by Thompson and a ‘plant pot holder’ by Cottle (who correlates it with Sowerby pattern 1135)
RD 298876 is described as a ‘jug’ by both - almost certainly the pattern 1125 'monkey-handled' creamer.
My reference photos of pieces bearing the lozenge for 6 March 1876 would seem to suggest that RD 298874 is the covered ‘monkey’ butter dish (pattern number 1125).
There is, however, also a covered marmalade jar (pattern 1203) bearing the lozenge to be accommodated somewhere in the RD bundle.
Which leaves either RDs 298870 or 298872 for your ‘elaborate sugar’.
Unfortunately, the covered ‘monkey’ pedestal sugar’ (pattern 1125) also still remains to be accommodated - it is certainly an ‘elaborate sugar’, (so could be RD 298872) but is most probably covered under the RD 298874 [?] ‘monkey’ butter dish specification.
After all that, the Sowerby pattern number for your sugar seems to be currently unknown, and a definitive answer to the RD number that corresponds to your sugar bowl still hangs in the balance (possibly lurking amongst the design representations).
Even then, the elusive form of RD 298870 still awaits discovery.
Fred.