Thanks Ivo, I've had a very good look at both bowls under different light sources but can't see any marks.
Anyway, here's the blue bowl. It measures 30.5 cm (12 inches) in diameter. Has fewer lobes than the yel;low bowl, but is similarly light and delicate. Although it doesn't show so well in the photos, the surface has been iridised. It has a bright shiny soap-bubble like appearance in the centre, shading into a matt, stretched iridescence towars the rim. Pontil mark shows 6 points of attachment, neatly snapped.
Thanks,
Steven