Watch List notes:

George III, proof halfcrown, 1817, small laureate head right, rev. crowned shield within Garter, reeded edge (S.3789; ESC.2097), certified and graded by NGC as Proof-63, well-set grey toning, rare
The only one graded as Proof-63 by NGC, two graded higher.

Estimate: 4500 - 5000 GBP