Watch List notes:

British Coins, Victoria, halfpenny, 1864, experimental type with numbers in obverse fields, young bust l., '250' engraved in l. field and '99' engraved in r. field, rev. Britannia std. r., with shield and trident (cf. S.3956), extremely fine and extremely rare, believed unique
*ex Gregory Collection, Baldwin's Auction 44, 2 May 2006, lot 577 (800-1000 GBP)