Here are some photos of a triangular flower trough by Jane Webb & Joseph Hammond acting &c… RD 263540, 21 July 1872 – Parcel 6.
It has the same vertically ribbed sides, beaded top edge, and beaded base as Rob’s boat trough shown in the opening post of this thread.
I think that it is quite probable that Jane Webb &c made a version of the boat trough to match the triangular flower trough (and perhaps other similar pieces within a range of troughs). The original plunger could have been used to fashion the interior, and the mould for the ‘clinker-built’ exterior either exchanged or modified to make the ribbed version of the boat trough.
The frosting on the exterior of the ‘clinker-built’ version would, of course, have been applied using hydrofluoric acid after the trough was removed from the mould and could easily have been an optional finish.
Fred.