Ivo:
I think you have an earlier Rainbow decanter than the one in the Della's link . I wouldn't have thought an escaping strand would make it a second, but as it's not signed, perhaps.
David
PS. Having just read Adam's post, which was made while I was writing, I'll add that I think that the 'Rainbow' series with the white background was started in 1982 and the clear in 1983.