pre owned sub: AD or independent watchmaker?

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I am in the market for a used Submariner. I found a local watchmaker (non AD) with a 14060 with box and papers. I also contacted the local AD and they would locate one for me. Its very possible these people do business with each other and buying through the AD would result in a markup, which i am hoping would just be a 10% finders fee. 100% original/authentic is important to me. Would the AD authenticate? Anyone do this before? Is the authorized dealer some sort of sacred bond that makes them beyond reproach... Clearly I have trust issues. Please help!