Hi Roy,
Your bowl looks very much like WMF Ikora-Medusa. But the 1931 WMF catalogue says that Medusa is lemon yellow in colour. In the book by Burschel & Scheiffele on page 122, pattern number 70/3450 is very like your little bowl. The book doesn't give the size, but the proportions look right. Page 116 there is a better picture of Medusa and it is very like your bowl. But, as you say, Medusa and Loetz Schaumglas can be confused.
Hope this helps.
Anton