I've "served my time" in the back rooms of Oxfam sorting, cleaning and pricing the bric-a-brac.
It is amazing how easy it is to "marry" all sorts of odd things, how easily some completely unrelated things fit others. I really wouldn't read anyting into the "fit" of the two bits.
They do both seem to have a pearlescent surface treatment. Do they actually match, in terms of the pearlescence?