Thanks to all. When I bought it, I hoped it might be a Dexel egg. When I got home, however, all the photos of the egg in the WMF book seem to show that they are cased in clear, with the clear most obvious at the base. My piece doesn't have any clear at the base. Paul, is the absence of clear at the base one of the variations that you would expect?
So I won't rule out a Dexel egg, but I'll look at the other suggestions as well.
Thanks again,
David