Great Britain
George III gold Half Guinea 1772, S-3732, 2nd Bust, "extremely rare" declares the SCBC, "Genuine Tooled - F Details" PCGS. The cataloguer sees no evidence of tooling, but the coin has been sweated to remove gold and is deeply scratched and cleaned. Nevertheless it is of exceptional rarity; the last sale we can find was of an uncertified piece graded Fine with scratches in a St. James's auction of June 2007, which sold for £3,100 or approximately $6,100. This one seems tempting at our estimate.
Estimate: 1500-2000 USD