Stu
I have had several of these over the years in yellow pearline and my first thought would have been Davidson or Henry Greener , but as Anne said Davidson did not make this colour but Henry Greener did, I think Henry Greener made quite a large range of items in this colour from baskets , plates and I have even had a signed lidded butter dish in this colour although in a different pattern, so I cannot be 100% sure but my best bet on your shell would be Henry Greener unless someone else tells you other wise
Roy