About 12 months ago I had a bloke with a dozer push a dam into my bottom paddock and where this thing come from had about 2feet of earth taken of the top. Yesterday I was playing around with my new detector, gm1000, and found this at a depth of around 6 inches. Wouldn't have a clue what it is but I would hazard a guess that it has been there for a while. It looks like some sort of cap to something. Can anybody shed some light on what it is? It is about 1 inch diameter.