Thank you, Barry - I think that you are correct.
I've checked my other reference photos for Henry Greener RD 284695 of 27 August 1874 - Parcel 9. There is another 12 inch dish in the same design, and I do have the matching design representation drawings (showing a plate in this case) from Paul Stirling & TNA.
I've also checked the Sowerby design representation for their RD 284431 of 17 August 1874 - Parcel 5 (which shows a lidded butter dish with stippled panels and a scalloped border) and, although there are some similarities the Henry Greener's RD 284695, I don't have photos of another actual Sowerby item in the pattern to confirm it.
There is a Sowerby lidded butter shown on the Thistlewood Sowerby CD-ROM Vol 1 (middle of the bottom row on page 4 of Sowerby pattern book XI, 1885) that corresponds fairly closely to the Sowerby RD 284431 design representation, but unfortunately the Sowerby pattern is cropped from the illustration.
I will amend the entries on the GMB RD database and the Glass Gallery Sowerby Album accordingly, and also include a link to this GMB topic for this additional information.
Fred.