Watch List notes:

Decimal Trials | Elizabeth II (1952-), Royal Mint Pattern Trial Planchet for a 50-Pence, c. 1967, by Hugh Graham Conway, on a dodecagonal flan, struck in Cupro-Nickel (Cu 75%; Ni 25%), 50 spaced 1mm. apart, rev. 50 spaced 1mm. apart, plain edge, 29.0mm., a handful of light surface marks, otherwise lustrous, practically as struck, an early Royal Mint trial for the denomination and presumed unique to commerce, with NGC Metallurgical Analysis Certificate (6135255-012).
From the EJ Thorne Collection
Estimate: £500 - £800