I purchased this piece a few weeks ago at auction, from a Danish shipment - as I loved the modernist form, and the superb glaze and decoration. It is a large centre-piece bowl and quite a heavy piece (although hollow formed).
I am pretty sure it is from Michael Andersen & Son Denmark as the glaze is identical to several pieces of MA&S that I have had before - a beautifully satin smooth mottled green. The way the foot is painted after firing also I've seen on several Danish pieces - not sure why or by whom (the owner or the factory?) as I cant think why you would want to try to disguise the base.
I have never seen a piece of MA&S without a stamp though - so I am intrigued if it is, then why no stamp. The only mark is the X and 1 which usually refers to who finished the piece in the factory. You often see X1 on Royal Copenhagen pieces in addition to the Designers stamp and other markings.
The design in the centre of the bowl really brings the piece to life.....a very mid-century, modernist design.