I have seen these in both clear with opalescent and yellow opalescent (vaseline opal/primrose pearline - depending on your continent or country of origin). I have looked long and hard for vaseline opalescent (yellow uranium opalescent) by Sowerby, and only one piece has been found: an open salt, kettle shape, with two little handles and a raised diagonal pattern on the outside. It is marked with the Sowerby logo on the base.
It is my belief that this wall-hanger is a Burtles, Tate, and Co. product. It follows similar design features by Burtles, Tate & Co, as far as the design, motif, and how their opalescent glass 'looks'.