[Zope] unique ID of object

I need to be able to uniquely identify a zope object by another way other than its context and id. I want to be able to create an object and then identify that object again even if it has been moved in the zope tree. I assume that each zope object must have some totally unique id that I can call somehow. I could write a routine that generates random ids that would be almost unique, but I am wondering if Zope has such a feature already built in somewhere. Tom