Roy, the Davidson RD 153858 (1891 Suite) blue pearline sugar and creamer are certainly uncommon.
On page 74 of Raymond Slack's "English Pressed Glass 1830-1900" there is a 4-sheet colour advert from the Pottery Gazette of 1 April 1893 showing Davidson's primrose pearline and blue pearline pieces. The advert shows 5 pieces in blue pearline corresponding to the RD 153858 (1891 Suite) - a 4-piece water set (comprising a large jug, a pair of tumblers and an underplate/tray), plus a lidded biscuit box (with, I think, an attached underplate). I can't remember seeing photos of actual examples of any of those advertised RD 153858 (1891 Suite) shapes.
There are no 1891 suite pieces in the primrose pearline sheets from the Pottery gazette advert.
By the way, I have never seen any Davidson RD 153858 (1891 Suite pieces) in plain blue (with or without RD numbers) either.
Fred.