Thank you for showing these, Paul. I will add them to the GMB RD database and the Glass Queries Gallery's Sowerby album in due course.
It certainly confirms that Mike's sugar bowl is indeed from Sowerby RD 260404 of 12 February 1872.
As for Sowerby RD 204605, also registered on 12 February 1872 - I can find no matching pattern number for the sugar bowl or, for that matter, any other shape, in Sowerby's pattern book XI (1885). Presumably, if they were ever illustrated in a previous Sowerby pattern book, then that pattern book is not available for reference in the public domain.
Fred.