Watch List notes:

George IV, proof halfcrown, 1825, bare head left, rev. crowned helmet over shield of arms, reeded edge (S.3809; ESC.2372), certified and graded by NGC as Proof-64, even grey toning, very scarce so nice
Only one other graded as Proof-64 by NGC, two graded higher.

Estimate: 3000 - 3500 GBP