Thread per object

I was hoping someone could settle this question for me . . .

If the Threading Model of an ActiveX Exe is set for Thread Per Object, does that mean individual threads per externally created objects only?

What I'm trying to find out is if a public class in the exe instantiates a private class from the exe, is there only the one thread for both now, or two? Would using async callbacks between the public and private objects allow for seperate threads between them?

Thanks!