As with many of these 'black' pieces, it isn't in fact, and shows as a very deep purple under strong transmitted light. Davidson is not something that I'm usually any good at, and often fail to find a matching illustration on the Stewart's web site - but believe I've seen this one described as pattern 535 bowl, from the 1960's, but I could be wrong. Must admit I don't find the colour to be common, and prefer black when it comes in a matt version, but just thought I'd show this as it seemed a bit unusual, and although this design seems to be late in the Davidson timescale, suppose it's on a par with Bagley 'Jetique' which was also around the same period (late 1950's and '60's) - perhaps there was a fetish for black at the time, but not that I can recall. Diameter is about 10" (255mm) maximum.
Grateful if someone will confirm if I have the design/pattern No. correct - also if anyone knows when it first appeared.
thanks for looking.