Great Britain
George V Proof Florin 1931 PR64 NGC, Royal mint, KM834, S-4038, ESC-3788 (R6 - "not traced"). Struck as a 'proof of record', and thus extremely rare, with tone-free surfaces that showcase even reflectivity and fully pronounced detail. While the crown of this date seems to appear once every five years or so at public auction, this is the first appearance that we've seen of the florin.
Estimate: 2000-3000 USD