In layman's terms I believe that means you have Jack. I've been privy to some pretty exciting Jesus on a potato chip discoveries, too, but was not convinced of the theory that Jesus was the original founder of the Lay's corporation. Confirmation Bias can be a beech, it's clouded the vision of many a treasure hunter and conspiracy seeker alike.
I don't believe anyone contested the age of your medallion, just the marks upon it that were clearly of a more recent vintage. Therefore, as a representation of an ancient artifact, I would naturally be forced to call twiddly dinks. No offense intended, no suspect declared. Again, Confirmation Bias can be a troublesome little twitch of the ego. I'm sure the individuals responsible for all the false treasure marks and faked petros covering AZ, NM, UT, were aware of that shortcoming in their fellow man. Though not confined to those areas alone, the sheer number of them concentrated there bears noting and always suspect. Your opinion of my "expertise" matters not, but your mention of it speaks volumes as to your own.
Good luck in your journey, may it bear fruit and good fortune.