Watch List notes:

(x) NGC MS64 | George V (1910-1936), Specimen 'Rocking Horse' Crown, 1935, .500 Fine Silver Proof, bare head left, rev. St George and Dragon, incuse lettered edge, 12h (Bull 3652; ESC 376; Spink 4049), a carbon spot to reverse, otherwise lustrous mint surfaces suggestive of the Specimen striking, virtually as struck, in NGC holder graded MS64 (Cert. #2790988-004).
The cataloguer is of the opinion this is a specimen striking, not a 'currency' striking given the visual register of the fields, far removed from the matte dull texture of the business issues.
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https://www.ngccoin.com/certlookup/2790988-004/64/
Estimate: £100 - £150