copying an index

I want two indexes, each with the same set of elements in the same order.  So I figured I could use Subset to do it, by taking a subset according to a criterion that is always true:  Idx := ['a', 'b', 'c']   and CopyIdx := Subset(Idx,1,Idx).  But I don't get letters in CopyIdx, I get numbers.  What gives?  How do I get a copy?