So I look at the volume status and I get this:
swtoast> vol status Volume State Status Options vol0 online normal root vol0 offline foreign partial
Hmm. At least in 5.0, it would, at least in some situations, prepend a "subscript" of the form "(1)" to the names of foreign volumes that would otherwise have a name identical to a native volume, so that you *could* delete or rename such a volume.
I'll have to check to see what happened to that....