What happens if the ProgId of my com object is not unique?

Question

Here's my class definition:

[ProgId("MyProject.MyClass")]
[ClassInterface(ClassInterfaceType.None)]
[Guid("...")]
[ComVisible(true)]
public class MyClass : IMyClass
{
  ...
}

What happens if a com client tries to create my object by the ProgId and there is randomly another one with the same ProgId?