I recently bought this lovely Monart bowl. I suspect it's a post-war piece as I can't find the colour combination in the pre-war colour code images shown on Frank's site, also the base has a very wide polished ring which I seem to recall has been discussed as being generally a sign of later production.
It measures approximately 8 inches (just over 20 cm) in diamter. It's a really beautiful item - the rim has a lot of aventurine while the centre is a pale sky blue.
Any further info as to approx date and colour code would be much appreciated.