Watch List notes:

William IV, proof halfcrown, 1831, bare head right, rev. crowned shield of arms on mantle, plain edge (S.3834A; ESC.2477), certified by NGC as Proof Details, Repaired, and yet the portrait is bold, the mirror lustre is strong and the overall appearance is rather pleasing; mintage of 300 for the coronation proof sets, rare

Estimate: 750 - 1000 GBP