The Conway Stewart Dinkie fountain pen was made, in a bewildering variety of styles and finishes, from the early 1920s up until 1972. This pen, the 'Dinkie 550' is a 1950s version.
The colour is described as 'marbled blue with brown flecks and veins' by Jonathan Donahaye in his seminal Conway Stewart classification. I think it describes it pretty well. The marbling is a combination of pale pearl blue to deep purple and the flecks and veins vary from gold to deep brown. The surface is excellent and has a clear barrel imprint, the Gold filling on the cap stud, clip, cap band, and filler lever is similarly pristine.
The Dinkie is a small pen and most users find it much more comfortable to write with the cap 'posted' on the end of the barrel. The pen fills well and the 14Ct. Gold nib writes with a medium line and a small but pleasing amount of flex. The line variation would allow someone with a decent 'hand' to produce impressive results.