Hi Valdiman, Not a coin but actually a token. These were minted at the Soho Mint in Birmingham, England sometime between 1820 to 1840. The exact date is unknown. The date on the token, 1783, commemorates the end of the Revolutionary War. The exact reason these were made is unknown. Yours is the Large Military Bust and would grade in the F15-VF20 range. Looks more like grime and encrustation but a TPG would probably label it as corrosion.