Yes I was a bit skeptical too Zig, but there is a good likeness so it might have led to something close to it. The main difference I can see is the long pedicel on yours but the photo I linked to which is obviously in Asia does have a pedicel.
Wiki gives info on Allamanda but I guess you have checked that already, they are highly sensitive to frost but we all grow plants on the edge.
http://en.wikipedia.org/wiki/A...
Waiting to see what you come up with from the knowledgeable plants person. The people growing it don't have any ideas at all?