not to say that this one was pressed in March 1888, but it's a tad knocked around so might have been made not too long after that date - carries the peacock and the Rd. No. in quite sharp outline, on the bottom of the inside.
For some reason Thompson omits this Reg. No., but it's in Ray Slack's book - I don't have any Kew Archive pix for this, but always a chance that it was Registered as CLASS 4 which might account for Thompson's omission. Because of the flat and shiny areas on the top, base and all six sides, would appear these have been ground/polished after pressing so has a slight look of quality and the design appears in the 1895 factory Pattern Book XV as pattern 1974 - 'a hexagon available in two sizes' - but doesn't tell us what the sizes were. This one measures c. 3.25 inches across the widest part and has a nice touch of beveling around the top edges.
I did try punching the factory and Reg. No. into the Board's search, but nothing came up, so seems it's not been on the Board previously. I shall be at Kew some time in the coming two or three weeks so will try snap the original factory drawing or whatever, and post here.
Credit for all the pattern book information is due to the Thistlewoods for their work on all the Sowerby factory information - this one is on the CD Volume 1 - Victoria to George V.