So sorry to hear that their decision wasn't in your favor, but thanks for being open about it. 

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As promised I'm to share the latest status as my case progresses. The aftersales team from my boutique forwarded me the result from the latest assessment. Long story short - worse did come to worst.
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"As requested, we have escalated your concerns to our After-Sales Department in Paris. Our After-Sales Directors have confirmed that the handbag in question has indeed not been manufactured by Hermès Paris. The Letter of Expertise and Affidavit will be issued to you shortly."
Not sure what else I could do to further my case at this stage. My store has done all they can to appeal to HQ. I have also submitted all I had on my end. I would imagine the letter will explain in more details who has examined the bag and what procedure has been carried out.
Feel like I should just cave in, pack my learnings and move on. Always buy directly from the boutique; Keep the receipt for life; Let go of any specific style that you missed.) After all without the original purchase document what else could I do?
I read that Hermes made a decision here. However it is incorrect. I stand by my opinion that this is an authentic Hermes manufactured Kelly Sellier Mou. All aspects are compliant with an authentic handbag of that description and I own two myself.
It is well known that Hermes after sales has frequently made errors, repairing counterfeits and declaring authentic bags not compliant. This recent occurrence is one of the worst instances I have known of and its result appalling.