I'd check the area thoroughly, far and wide HM, just incase it's not a loner,... the authorities wouldn't want to acknowledge it anyway as it wouldn't fit in with their story about Australia, they'd have to be dragged kicking and screaming to an understanding of acknowledgement. Maybe take a sieve and do a soil sifting of the immediate area that you found it and then a few scattered test areas around the vicinity of the find, just incase there are some artefacts in the soil that will not come to light with the aid of a metal detector, but may in fact require a much more fastidious search method.
Have a good look at the lay of the land and use your imagination to help you out a bit.
Good luck with it all, I for one hope it's the real deal,...keep tight lipped about its whereabouts and have a bit of fun.
Keep a detailed plan of what you find where(think like an archaeologist) as that could be important.
Take a few choice photos along the way that can't show where you are, but gives a working view of what you are doing so we can enjoy it with you.
Cheers and Beers.
Silver.
