I suspect you stumbled onto this, too, but I read this same statement in a few online resources (emphasis mine): "This would appear to be a vicuna coat since it has the label "King's Vicuna". Oxxford's cashmere coats are labelled "Emperor's Cashmere." Another way to check is to look at the shop ticket in the pocket behind the inside chest pocket label." I see it says Emporer's cashmere, but I wonder if that is a clue to the content of the fibers...that is, perhaps it is a blend of cashmere and vicuna. Also, did you ask Oxxford: Code: https://www.facebook.com/OxxfordClothesInc/
You are so fortunate to own a real vicuna coat. While I cannot add anything about the coat's history, I wanted to add my guess concerning your question on the difference between the "King's" and "Emperor's" labels. Traditionally, an Emperor is of higher status than a King, so my guess is that the Emperor vicuna is of a better quality or grade. Of course, all vicuna is wonderful!
Please be aware that Vicuna is now an endangered species, and so there are legal issues with selling clothing made from Vicuna - even if it was made a long time ago. Most Vicuna is on Appendix I of CITES, the most controlled, and so the controls in place are the same as, for instance, leopard fur and elephant ivory. Certain managed populations of Vicuna today are listed under Appendix II, and so can be traded, but are still under strict controls needing licensing and certification for legal sale. However as your coat was not produced under those more recent conditions, I believe you would have to treat it as Appendix I. The exact details vary according to where you live, but it is very difficult to legally sell anything made from an CITES Appendix I animal.
