Great Britain
George III gold Guinea 1763, S-3726, 2nd laureate Head, very rare type, AU Details "Surface Hairlines" NGC, but despite its altered surfaces this rare guinea is bold in all details and was clearly without wear when its surfaces were "adjusted." The custom a century ago was to dip coins into bowls of diluted acid in order to brighten them, and this appears to be what happened to this rare coin.
Estimate: 4000-6000 USD