I don't think it is Davidson, but I KNOW it is not American! I had always thought that this was an unidentified BURTLES, TATE, & CO. I have one in Primrose Pearline. I am thinking Burtles, Tate made it to compete with Davidson during the time period that Davidson made RD 176566. I have also seen one of these (in blue opalescent) that had a figural girl in spelter metal as a stand, and this was an umbrella/bumper shoot that upturned on her in the wind. It made a cute piece. It was being sold by a seller in England. I have also seen several of these that came out of England in Primrose Pearline. in OPALESCENT GLASS by Edwards/Carwile, 5TH EDITION, they gave it a name of DAISY SWIRL, and suspected it was Davidson, but did not know. By process of elimination, Davidson's patterns are fairly well researched and it does not show up. Sowerby made very very little primrose pearline (a two handled salt or small sugar with swirls comes to mind) and Greener's patterns are also pretty well known. My most educated guess is either Burtles or Greener. When you sell it, you *could* use the name of DAISY SWIRL, unidentified British Blue pearline/opalescent.
mr. vaseline glass