Great Britain
George IV gold Proof Sovereign 1821 PR61 Cameo NGC, Royal mint, KM682, S-3800, WR-231. A highly collectible proof. Wilson and Rasmussen gives it a rarity rating of R3, meaning that they think there are just a couple dozen examples of this type in existence. This is the right amount where there are enough available so that it is a known and popular type, but rare enough so that there is always heated competition when one comes to market. Reflective fields and a light cameo effect makes this coin rather pleasing in hand.
Estimate: 5000-6000 USD