u/AmbivalentFanatic

I am a metal detectorist and I dug this coin in a field where I've found a number of other Colonial coins and artifacts from the 1750s onward. I am in Nova Scotia Canada, so the coins I find are British (and very rarely French). This coin is completely encrusted in what I presume is silver sulfide. I suspect this might be a silver sixpence from the reign of either George II or III (I have found coins from both eras in this field). I have been wrapping it in aluminum foil and boiling it in water and baking soda and it seems to be having almost zero impact. In fact nothing I do seems to have any impact. I am desperate to find out what this coin is. Is it possible?