For me, this question began with my dream of the Chinese woman. M said that that was my double.
Granting that he was right, I then looked at that woman and knew that I did not recognize her -- that her vibration and energy were completely different to the female I've seen, and most certainly different to the men that I've seen. The men, though differing all in appearance, have a wily, rapacious, almost smart-ass quality. The female I've met indeed has a sense of humor and mischief, but I would not call her wily or hungry in the way the men are. She has a worldly elegance to her if one looks closely, but if one settled for the first glance, one could mistake her for matronly.
The Chinese woman was dead sober and deadpan. She was very in sympatico with her horse, and I had a liking for her right away. But all I can tell you is that her essence varies greatly from the original female.
So ... either she wasn't my double, or, a new entity has been added, or discovered. I suppose one would just have to take my word for it that it was a completely different energy.
I've never entertained the notion of being a nagual myself, so I'm hard-pressed to blend that idea into my thinking yet. Still processing...