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 'squircle' flan, struck in Cupro-Nickel (Cu 79%; Ni 21%), 50 broadly spaced (4.5mm.), rev. 50 narrowly spaced (2.5mm.), 25.5mm., 11.29g, 12h, some light surface marks and fingermarks, otherwise lustrous and hints of toning, extremely fine, an early Royal Mint trial for the denomination, presumed unique to commerce, with NGC Metallurgical Analysis Certificate (6135255-011).
From the EJ Thorne Collection
Estimate: £500 - £800