Watch List notes:

(g) William IV (1830-1837), 'Lightweight' Proof Half-Sovereign, 1831, struck on the experimental small flan, by Wyon (after Chantrey) and Merlen, bare head right, plain truncation, rev. crowned shield on mantle, edge plain, 3.89g, 4h (Murdoch III, -; Nobleman 205/6(b); W&R 267 [R3]; Marsh -; Spink 3830), an evidently early or more probably original '1831 striking' with inverted die axes as customary for currency issues of the period, a wonderful example save only for a trace of cabinet friction in otherwise pleasingly brilliant fields, the central devices frosted cameo, almost FDC, rare, , This lot is also offered as a group lot in lot 280. Whichever reaches higher hammer price will sell and the other option will be withdrawn..
Provenance
The Gemini Collection
, ,
NGC PF62 ULTRA CAMEO (Certification #5880299-002)
, https://www.ngccoin.com/certlookup/5880299-002/62/
Estimate: £3,000 - £4,000