I recently bought this pressed glass dish from eBay because I was somewhat intrigued.
The listing said that there was an indistinct diamond registration mark, and an email to the seller revealed that the only detail that they could decipher was a 1 or I at the 6’oclock position. I thought the design was reminiscent of some of the early Greener designs, but initially I couldn’t find an exact match in photo references, so I bid a nominal sum for the dish as an inexpensive exercise in detection .
Now I have the dish, I’ve been able to ‘read’ the details on the diamond mark by the old-fashioned expedient of a pencil-rubbing on thin paper, revealing the identifying details as 31-H-I-8 (registered on 31 July 1869 – Parcel

. The registrant was Henry Greener, and the corresponding RD number 231430.
Both Thompson and Slack show a single design registration for RD 231430 [Thompson: ‘Design for a circular glass plate or stand (Gladstone”)].
At
http://1st-glass.1st-things.com/gallery-victorian/slides/dvgreenerflintplates.htmla plate in the ubiquitous Greener Gladstone design is shown alongside a plate with the same design as my dish, but which supposedly bearing the diamond registration mark with identifying details 7-H-A-7 (for 7 December 1869 – Parcel 7). This, in fact, corresponds to Greener RD 236921, which Thompson gives as the equally ubiquitous Greener ‘Peabody’ commemorative design, and which my dish is obviously not.
Does anyone else have Greener pieces with this ‘non-Gladstone’/’non-Peabody pattern and a diamond registration mark? If so, which date does ‘your’ mark translate to, please?